The editor actions which indent and comment code will accept a multi-line
selection which starts and ends in middles of lines, but SurroundWithTryCatch
doesn't.

If you have a single cursor and no selection SurroundWithTryCatch will
do it's thing on the one line the selection is in.

If you have more than one line, having gotten used to how indent
and comment work I figured a sloppy selection would do, but I got an error
    Cannot surround selected block with try-catch.

When I carefully selected the whole two lines it worked. 
I wold be more useful if it cold handle sloppy selection like indent
and comment ... seems like an opportunity for some code factoring.