[alteralto]

CurrentMapsetWatch.on_modified read GISRC with line.split(":"), which raises ValueError as soon as a value holds a colon. On Windows that is the usual case, GISDBASE: C:\..., so the watcher thread died there on the first change to GISRC and the Data panel stopped noticing mapset changes. A blank line raised as well.

GISRC lines are now split on the first colon, as read_gisrc in lib/init/grass.py and the other GISRC readers do, and lines without a colon are skipped.

Tested on Windows with wxPython 4.3.2 and watchdog 6.0.0: calling CurrentMapsetWatch.on_modified on a GISRC whose GISDBASE is C:\grassdata raises ValueError: too many values to unpack on main, and posts the mapset change with this fix. I didn't add a test to the repository: the wxGUI code has no pytest suite, and the pytest workflow doesn't install wxPython.

Fixes #8096