Show label creation errors

[ScreamingDev]

Turning a prepared label into a real one sometimes lead to an error. Unfortunately this problem was not shown to the user. Due to a type mismatch the message could not be displayed properly.

• Torn two greedy jQuery selector into simpler ones.
• Added missing semicolon which may lead to problems on IE9/8

Things to review

Common things:

• [x] Works fine.
• [x] Changelog written or not needed.
• [ ] In case of bugfix also merged in other minor versions.
• [x] No conflict with current branch.

Got an idea while looking at the GUI? Please add a new issue refering to this one.

[ScreamingDev]

for some reason the other problem is in this merge request too -.-