Don't allow empty card titles

[weeman1337]

• Resolves: Card Title can be empty and hence not be edited anymore #589
• Target version: master

Summary

• stores the titles temporarily when editing
  • if the new title is empty it restores the previous one
  • if the new title is not empty it commits the changes
• enables the browser form validations to work on "enter"

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [-] Tests (unit, integration, api and/or acceptance) are included
• [-] Documentation (manuals or wiki) has been updated or is not required

[codecov]

Codecov Report

Merging #611 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #611   +/-   ##
=======================================
  Coverage   76.07%   76.07%           
=======================================
  Files          57       57           
  Lines        2474     2474           
=======================================
  Hits         1882     1882           
  Misses        592      592

[juliusknorr]

Nice work. Thanks @weeman1337