Fix adding metadata to metadata groups

[solth]

Fixes #4464, fixes #4285

Edit: seems #4465 and #4457 aren't fixed after all

[Kathrin-Huber]

Issue #4457

[Kathrin-Huber]

Issue #4465

[matthias-ronge]

The right metadata appears to be available for selection at first. Adding also works. But I always have to click two times before the pop-up to open (the fundamental problem that we sometimes have in the metadata editor).

Another problem is, but I don't know whether this is related or a completely different problem, I just noticed: Whenever I click the delete metadata button, I first have to click away a Firefox warning whether I want to leave the page (no) and then again, then it usually works (but not always, and one time I got a warning for a validation error). But it can also be that this is a completely independent problem or it is due to my ruleset, maybe, I can't say that. I haven't been using the button for a long while.

[matthias-ronge]

[solth]

The right metadata appears to be available for selection at first. Adding also works. But I always have to click two times before the pop-up to open (the fundamental problem that we sometimes have in the metadata editor).

Yes, this has to do with the update being triggered by the javascript blur events (documented in #3821)

Another problem is, but I don't know whether this is related or a completely different problem, I just noticed: Whenever I click the delete metadata button, I first have to click away a Firefox warning whether I want to leave the page (no) and then again, then it usually works (but not always, and one time I got a warning for a validation error). But it can also be that this is a completely independent problem or it is due to my ruleset, maybe, I can't say that. I haven't been using the button for a long while.

That is a different problem and occurs in the master branch, too.

[solth]

Issue #4457

I think #4457 is about MetadataGroup children being unintentionally duplicated. Your screencast shows MetadataGroups directly assigned to a structural element being duplicated by accident. Looks like a similar problem, but not exactly what was described in the issue, IMO.