After hand-testing everything I could think of, including clicking outside the box after clicking inside, I applied the click (and Mac crash) fix to 3.7 and 3.6.  As far as I know, it should appear in 3.6.2rc whenever that appears.  If so, I hope people who verified the bug will download and try to verify the fix.

I will open separate issues for the following and list them on the autocompletions master issue, #27609.
Improve autocomplete tests.
Improve 'Completions' doc subsection.
Stop insertion of \n into text when closing box
 (see opening message above).
I will also post a message on #27609 about behavior issues mentioned here that are not part of any open issue.