Cast frame labels to strings everywhere they're used

[rreusser]

Numbers keep sneaking through as valid frame labels or animate arguments, which then cause animations to totally fail. They should be cast to strings on some sort of supplydefault step, otherwise we should cast them to strings every time they're used.

Until then, a note to avoid integer labels, cc: @Kully @jp and… @empet ? is that the right callout?

[etpinard]

@rreusser was this completed in #1236?

[rreusser]

Ah yes, I believe so. I think it's working fine. That PR was the day after this, so looks like a stray unclosed issue. 👍

[etpinard]

Great. Thanks. Closing.