A user reported an error message from this plugin on Krita’s bugtracker: 503485 – Unknown error pop up
File "%APPDATA%\krita\pykrita\lab_colour_picker\selector_common.py", line 155, in foregroundColorToLab
comp = fg.components()
AttributeError: 'NoneType' object has no attribute 'components'
I’m guessing the cause is that this plugin’s timer that checks the current foreground color is never stopped, so it may check when there is no document open and thus no current foreground color.