Misplaced period can cause a hang

(Bug, Closed -> Duplicate, Priority: Critical, Test Status: Unit tested , Reported By Bad Link: Thing 3y284oe not found, )

Summary: This is almost certainly another parser weakness, hopefully easy to fix.

Original report from Eric:

I accidentally put a period inside my [[ ]] and got a hang instead of an error:

[[Playtesters -> _showLink(""see the current list here"")PERIODHERE]]

Confirming it: if I go into the Explorer for a Thing and put in

_showLink(""link text"")PERIODHERE

I get an "unexpected error" message in the upper-right.

Note that this is sufficiently broken that it even kills the embed above; hence the PERIODHEREs.