Outros undefined when transitioning to another page

Couldn’t get a REPL repro but If I try to navigate from https://smelte-8z4ib07lj.now.sh/components/tabs to any other page I get this error:

index.mjs:629 Uncaught (in promise) TypeError: Cannot read property 'callbacks' of undefined
    at U (index.mjs:629)
    at Object.o (Waypoint.svelte:116)
    at hn (index.mjs:761)
    at Object.o (Image.svelte:27)
    at hn (index.mjs:761)
    at Object.o (tabs.c766b77c.js:1)
    at hn (index.mjs:761)
    at Object.o (TabButton.svelte:11)
    at hn (index.mjs:761)
    at Object.o (Tab.svelte:6)
</details>

At this line:

function transition_out(block, local, callback) {
    if (block && block.o) {
        if (outroing.has(block))
            return;
        outroing.add(block);
        **outros.callbacks.push(() => {**
            outroing.delete(block);
            if (callback) {
                block.d(1);
                callback();
            }
        });
        block.o(local);
    }
}

Works https://smelte-8z4ib07lj.now.sh/components/tabs

Doesn’t https://smelte-ocubxglhw.now.sh/components/tabs

Not sure what causes the error so I simply patched it by adding an extra check if outros.callbacks is set.

[nick-lehmann]

I can also confirm that the bug is still present in 3.28.0 and the workaround from @srinivasrk works. Until the bug is fixed, you can use @rollup/plugin-replace to automate this workaround

plugins: [
  replace({
    'outros.c.push': 'if (outros === undefined) { block.o(local); return }\noutros.c.push'
  }),
]

I know it is ugly and might break sometimes or something else, but it works for now (for me)…

[JefferyHus]

Issue is back as of 3.12.1, I am getting this error now when trying to transition to another page.

Cannot read property 'c' of undefined

function transition_out(block, local, detach, callback) {
    if (block && block.o) {
        if (outroing.has(block))
            return;
        outroing.add(block);
        outros.c.push(() => {
            outroing.delete(block);
            if (callback) {
                if (detach)
                    block.d(1);
                callback();
            }
        });
        block.o(local);
    }
}