UI: Fixes for repo topic editor

[silverwind]

• Properly hides the edit interface when saving a empty topic list
• Align the Done button with the edit box

Before

After

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@1772893). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master   #5971   +/-   ##
========================================
  Coverage          ?   38.7%           
========================================
  Files             ?     330           
  Lines             ?   48642           
  Branches          ?       0           
========================================
  Hits              ?   18827           
  Misses            ?   27088           
  Partials          ?    2727

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1772893...9d608b1. Read the comment docs.

[adelowo]

Maybe we can add a real a cancel button rather than only hiding the editor when Done is clicked and the content is empty

[silverwind]

When the list is empty, the user wants to clear out the list, just hiding without any action would be wrong. Now a always visible cancel button might be useful, but I'm not sure its really needed, re-saving works just fine.