this.handlers is undefined

Wavesurfer.js version(s):

4.1.0

Code needed to reproduce the issue:

Region plugin doesn’t load, check example page:

https://wavesurfer-js.org/plugins/regions.html

When calling this.regions.add(options). Line 199 of regions/index.js registers this event:

        region.on('remove', () => {
            delete this.list[region.id];
        });

Results in TypeError: can't access property "remove", this.handlers is undefined

Last change to observer: https://github.com/katspaugh/wavesurfer.js/commit/590d9ccc96f6c69090849f2e5cfb4587da647ee5 Looks like removing the lazy creation of handlers object broke the regions plugin.

Found this comment in observer.js: * plugins borrow part of this class without calling the constructor Can we do something about that without breaking existing plugins? Not calling the constructor doesn’t sound very good.

Worst case scenario we revert to what we were doing before.

[thijstriemstra]

4.1.1 was released and fixes this issue.

[thijstriemstra]

Or maybe we should revert 590d9cc. It was just code cleanup changes.

@sundayz please do.