I sent this report last night but it didn't go through, so I'm
re-sending.

While working on some JS code I noticed that when writing a certain
file, I got a "scan-error" when I typed TAB.  I tracked this down to a
buglet in js--indent-in-array-comp.

This patch fixes the problem by wrapping the call to forward-sexp there
in a condition-case.  I've added a new test case as well.