Created attachment 134980 [details]
screenshots

SUMMARY
Scroll bar may have wrong size when Kate was started by opening a file.
If file is opened from already started Kate ("File"->"Open...") - scrollbar will be displayed correctly

STEPS TO REPRODUCE
1. Open a file from file manager 
2.             from terminal: 'kate /path/to/file'
3.             from Kate ("File"->"Open...")

OBSERVED RESULT
if a file opened from file manager scroll bar is too small

EXPECTED RESULT
scroll bar height should not depend on the file opening method

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Manjaro KDE, testing branch
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.78.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Dolphin file manager