[2.3.3] Services - NTP - Settings: Prefer/No Select checkboxes invisible when adding entries
Best described with a picture:
- this only happens in 2.3.3 snapshots. 2.3.2 is OK.
- same issue with all themes.
- tested with Chrome v52 and FF v48.
Fixed #6788 by clearing only the first label in the cloned row
(cherry picked from commit d38d215d1d9429d3a1a15708f92b14cf3a15b247)