Resolve "TypeError: undefined is not an object (evaluating 'e.selectedRegion.name')"

Closes #1623 (closed)

What does this MR do?

• The ok buttons in the region tree dialog (in "Profil bearbeiten") and in the join region dialog (in the region menu in the topbar) disabled until a region is selected. This way the selectedRegion value can not be undefined.
• Renames the button from "Senden" to "Übernehmen"
• Makes the modal scrollable, which is more comfortable in a long list of regions

How confident are you it won't break things if deployed?

Quite sure that it won't break anything, but not absolutely sure that it will fix #1623 (closed)

How to test

1. Checkout branch locally
2. Login as userbot
3. Go to your profile page and select "Profil bearbeiten"
4. Click the button for selecting a region
5. Select a region in the modal

Screenshots (if applicable)

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• added to the next milestone (see https://gitlab.com/foodsharing-dev/foodsharing/-/milestones, unless it has a "for:Dev" label)
• added an entry to CHANGELOG.md
• added a short text that can be used in the release notes
• Once your MR has been merged, you are responsible to create a testing issue in the Beta Testing forum: https://foodsharing.de/?page=bezirk&bid=734&sub=forum. Please change the MRs label to "state:Beta testing".
  • Consider writing a detailed description in German.
  • Describe in a few sentences, what should be tested from a user perspective.
  • Also mention different settings (e.g. different browsers, roles, ...) how this change can be tested.
  • Be aware, that also non technical people should understand.

Release notes text in German

Closes #1623 (closed)