Created attachment 154131 [details]
Crash log from this error

SUMMARY
***
NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols.
See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
***


STEPS TO REPRODUCE
1. In Palette docker:
2. Open Palette Editor
3. Select value for "Columns of Swatches:", type "0" (zero)

OBSERVED RESULT
 Crash

EXPECTED RESULT
 Replaced with either 1 or original value

SOFTWARE/OS VERSIONS
Windows: 5.1.3
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
 Should be an easy fix, catch the exception and return it to its previous value (or 1 if you'd find that easier). Have a good {"Day", "Night"} // :)