NPE on config initialization - can't load saved marker file, if id contains a slash

Issue Description: Dynmap saves configuration just fine, but it might fail to load it and throw NPE. It looks like the culprit is here: https://github.com/webbukkit/dynmap/blob/v3.0/DynmapCore/src/main/java/org/dynmap/markers/impl/MarkerSetImpl.java#L469

for(String id : areamarkernode.keySet()) {
    AreaMarkerImpl marker = new AreaMarkerImpl(id, this);   /* Make and load marker */
    if(marker.loadPersistentData(areamarkernode.getNode(id))) { // BUG: .getNode(id) returns null

In my case it was cause by the area ID containing a / character.

• Dynmap Version: dynmap v3.1-beta3a-409
• Server Version: Paper 1.16.2 build 185
• Pastebin of crashlogs or other relevant logs: Are marker:

[10:14:53] [Server thread/INFO]: [dynmap] Enabling dynmap v3.1-beta3a-409*
[10:14:53] [Server thread/INFO]: [dynmap] Added 4 custom biome mappings
[10:14:53] [Server thread/INFO]: [dynmap] Using LuckPerms 5.1.66 for access control
[10:14:53] [Server thread/ERROR]: Error occurred while enabling dynmap v3.1-beta3a-409 (Is it up to date?)
java.lang.NullPointerException: null
        at org.dynmap.markers.impl.AreaMarkerImpl.loadPersistentData(AreaMarkerImpl.java:122) ~[?:?]
        at org.dynmap.markers.impl.MarkerSetImpl.loadPersistentData(MarkerSetImpl.java:471) ~[?:?]
        at org.dynmap.markers.impl.MarkerAPIImpl.loadMarkers(MarkerAPIImpl.java:717) ~[?:?]
        at org.dynmap.markers.impl.MarkerAPIImpl.initializeMarkerAPI(MarkerAPIImpl.java:384) ~[?:?]
        at org.dynmap.DynmapCore.initConfiguration(DynmapCore.java:410) ~[?:?]
        at org.dynmap.bukkit.DynmapPlugin.onEnable(DynmapPlugin.java:905) ~[?:?]
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.16.2.jar:git-Paper-185]
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:380) ~[patched_1.16.2.jar:git-Paper-185]
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:483) ~[patched_1.16.2.jar:git-Paper-185]
        at org.bukkit.craftbukkit.v1_16_R2.CraftServer.enablePlugin(CraftServer.java:499) ~[patched_1.16.2.jar:git-Paper-185]
        at org.bukkit.craftbukkit.v1_16_R2.CraftServer.enablePlugins(CraftServer.java:413) ~[patched_1.16.2.jar:git-Paper-185]
        at net.minecraft.server.v1_16_R2.MinecraftServer.loadWorld(MinecraftServer.java:468) ~[patched_1.16.2.jar:git-Paper-185]
        at net.minecraft.server.v1_16_R2.DedicatedServer.init(DedicatedServer.java:241) ~[patched_1.16.2.jar:git-Paper-185]
        at net.minecraft.server.v1_16_R2.MinecraftServer.w(MinecraftServer.java:939) ~[patched_1.16.2.jar:git-Paper-185]
        at net.minecraft.server.v1_16_R2.MinecraftServer.lambda$a$0(MinecraftServer.java:177) ~[patched_1.16.2.jar:git-Paper-185]
        at java.lang.Thread.run(Unknown Source) [?:?]

Circle:

[15:08:36 INFO]: [dynmap] Enabling dynmap v3.1-beta3a-409*
[15:08:37 INFO]: [dynmap] Added 4 custom biome mappings
[15:08:37 INFO]: [dynmap] Using Bukkit Permissions (superperms) for access control
[15:08:37 INFO]: [dynmap] Web interface permissions only available for online users
[15:08:38 ERROR]: Error occurred while enabling dynmap v3.1-beta3a-409 (Is it up to date?)
java.lang.NullPointerException: null
	at org.dynmap.markers.impl.CircleMarkerImpl.loadPersistentData(CircleMarkerImpl.java:104) ~[?:?]
	at org.dynmap.markers.impl.MarkerSetImpl.loadPersistentData(MarkerSetImpl.java:509) ~[?:?]
	at org.dynmap.markers.impl.MarkerAPIImpl.loadMarkers(MarkerAPIImpl.java:717) ~[?:?]
	at org.dynmap.markers.impl.MarkerAPIImpl.initializeMarkerAPI(MarkerAPIImpl.java:384) ~[?:?]
	at org.dynmap.DynmapCore.initConfiguration(DynmapCore.java:410) ~[?:?]
	at org.dynmap.bukkit.DynmapPlugin.onEnable(DynmapPlugin.java:905) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.16.2.jar:git-Paper-185]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:380) ~[patched_1.16.2.jar:git-Paper-185]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:483) ~[patched_1.16.2.jar:git-Paper-185]
	at org.bukkit.craftbukkit.v1_16_R2.CraftServer.enablePlugin(CraftServer.java:499) ~[patched_1.16.2.jar:git-Paper-185]
	at org.bukkit.craftbukkit.v1_16_R2.CraftServer.enablePlugins(CraftServer.java:413) ~[patched_1.16.2.jar:git-Paper-185]
	at net.minecraft.server.v1_16_R2.MinecraftServer.loadWorld(MinecraftServer.java:468) ~[patched_1.16.2.jar:git-Paper-185]
	at net.minecraft.server.v1_16_R2.DedicatedServer.init(DedicatedServer.java:241) ~[patched_1.16.2.jar:git-Paper-185]
	at net.minecraft.server.v1_16_R2.MinecraftServer.w(MinecraftServer.java:939) ~[patched_1.16.2.jar:git-Paper-185]
	at net.minecraft.server.v1_16_R2.MinecraftServer.lambda$a$0(MinecraftServer.java:177) ~[patched_1.16.2.jar:git-Paper-185]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_262]

• Other Relevant Data/Screenshots: Nothing
• Steps to Replicate:

1. Start fresh server, with new dynmap.
2. Run: /dmarker addcircle id:prof/bloodstone
3. Stop the server
4. Start the server and observer errors being thrown in dynmap onEnable

[X] I have looked at all other issues and this is not a duplicate
[X] I have been able to replicate this

[FedUpWith-Tech]

Just kidding. Its fixed on 3.3beta3 at least:

%YAML 1.1
---
icons:
    monkey:
        label: monkey
sets:
    markers:
        hide: false
        circles:
            prof/bloodstone:
                markup: false
                fillOpacity: 0.35
                strokeWeight: 3
                label: prof/bloodstone
                fillColor: 16711680
                world: world
                x: 100.0
                zr: 1.0
                y: 85.0
                z: 100.0
                xr: 1.0
                strokeColor: 16711680
                strokeOpacity: 0.8
        deficon: default
        areas: {
            }
        label: Markers
        markers:
            monkey:
                world: world
                markup: false
                x: 4.0
                icon: monkey
                y: 85.0
                z: 5.0
                label: monkey
            test/marker:
                world: world
                markup: false
                x: 100.0
                icon: house
                y: 85.0
                z: 100.0
                label: test/marker
        lines: {
            }
        layerprio: 0
playersets: {
    }

No errors in console

[10:03:05 INFO]: [dynmap] Enabling dynmap v3.3-beta-3-591
[10:03:05 INFO]: [dynmap] Added 18 custom biome mappings
[10:03:05 INFO]: [dynmap] Using Bukkit Permissions (superperms) for access control
[10:03:05 INFO]: [dynmap] Web interface permissions only available for online users
[10:03:05 INFO]: [dynmap] Mod Support processing completed
[10:03:06 INFO]: [dynmap] Loaded 25 shaders.
[10:03:06 INFO]: [dynmap] Loaded 82 perspectives.
[10:03:06 INFO]: [dynmap] Loaded 22 lightings.
[10:03:06 INFO]: [dynmap] Starting enter/exit processing
[10:03:06 INFO]: [dynmap] Finish marker initialization
[10:03:06 INFO]: [dynmap] Web server started on address 0.0.0.0:8123
[10:03:06 INFO]: [dynmap] version 3.3-beta-3-591 is enabled - core version 3.3-beta-3-591
[10:03:06 INFO]: [dynmap] For support, visit https://reddit.com/r/Dynmap or our Discord at https://discord.gg/s3rd5qn
[10:03:06 INFO]: [dynmap] To report or track bugs, visit https://github.com/webbukkit/dynmap/issues
[10:03:06 INFO]: [dynmap] If you'd like to donate, please visit https://www.patreon.com/dynmap or https://ko-fi.com/michaelprimm
[10:03:06 INFO]: [dynmap] Loaded 3 maps of world 'world'.
[10:03:06 INFO]: [dynmap] Loaded 2 maps of world 'world_nether'.
[10:03:06 INFO]: [dynmap] Loaded 2 maps of world 'world_the_end'.
[10:03:06 INFO]: [dynmap] Enabled
[10:03:06 INFO]: Running delayed init tasks
[10:03:06 INFO]: Done (2.790s)! For help, type "help"

And the marker does show up on the map:

I’ll re-mark this as fixed and close. Nice catch @JurgenKuyper

[FedUpWith-Tech]

This can still be replicated in the most recent versions