fix bad handling of exceptions that are false after being chomped, or st...

...ringify to false

Since we were stringifying and chomping $@ before checking its original value,
exceptions consisting of "\n" or "" (or have a string overload that results in
one of these values), were giving the appearance of the test merely exiting
early, which is treated as "tests pass, but the remainder were skipped" rather
than properly being treated as a failure.