Destroy modals before leaving

[danieldiekmeier]

The current modal implementation has two bugs. They both surface when you …

1. Open a modal
2. Navigate away (e.g. with a link inside the modal)
3. Go back (e.g. with the browser's back button)

The two bugs are:

1. Shimmer will add a new .modal-blind every time, making the blind continuously darker
2. The "close" click handler will not be added again, making it impossible to close the modal

This is in Recordsale when trying to add an album to my wantlist even though I'm not logged in, then clicking the back button:

To solve this, I added code to immediately destroy all open modals. I thought it's probably not worth writing a bunch of code to try and "rehydrate" the modals on back navigation. I also added a check to only contain a new .modal-blind if we don't already have one.

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I decided on this way to keep the changes and the chance for breakage minimal. If we want to keep modals open when coming back, I'd say we should maybe migrate modals to Stimulus, so Stimulus can handle all the event handlers for us.