Support toggle comment without selection
Address T68062 for comment, indent is already mostly working
This crashes if you run it on a blank line of text, then try to type something.
This was wrong, caused undo to fail.
I have updated the diff, but I'm not sure that's enough as I was not able to reproduce the crashes as you said
Thanks, committed rBc3a9fc5efb4a81f6efb28d0c787e17503deaee46