Add fallback timeout to reset `modalClosing` flag in `ModalManager`

[iPurpl3x]

Changes proposed in this pull request:

• Added a fallback timeout to the animateHide function to ensure the modalClosing flag is reset. This change aims to prevent potential issues where a modal could become unresponsive if the modalClosing flag remains set to true.

Reviewers should focus on:

• The implementation of the timeout in the animateHide function.
• Ensuring that the addition of the timeout and the clearTimeout call do not introduce any regressions or unintended side effects.

QA

Necessity

• [x] Has the problem that is being solved here been clearly explained?
• [x] If applicable, have various options for solving this problem been considered?
• [x] For core PRs, does this need to be in core, or could it be in an extension?
• [x] Are we willing to maintain this for years / potentially forever?

Confirmed

• [x] Frontend changes: tested on a local Flarum installation.
• [ ] Core developer confirmed locally this works as intended.
• [x] Tests have been added, or are not appropriate here.

[iPurpl3x]

@SychO9 can you explain why this got closed?

[imorland]

@iPurpl3x I would guess because it's targetting 1.x? Other than fixes, 1.x is more or less in feature freeze. I'm sure if you could retarget for 2.x we could accept this change 🤔

I'll wait to see what @SychO9 thinks also...

[SychO9]

I deleted the 1.x branch to replace it with another to cleanup a few commits when working on the extension manager which is what seems to have auto closed this on delete.

reopening but we are pretty much only patching critical issues for 1.x to focus on 2.x development. We could include this in a patch should anything else (or more fixes) turn up for core as well but we unfortunately don't intend to make a new patch for every 1.x PR 🙏🏼, I hope you understand that just wouldn't be feasible.