Don't confuse errors with nil in bytecomp-tests.el

* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-check-1)
(bytecomp-explain-1, test-byte-opt-arithmetic, bytecomp-lexbind-check-1)
(bytecomp-lexbind-explain-1):
If an expression raises an error when evaluated, don't treat it as if
it had succeeded with the value nil; use 'bytecomp-check-error' as the
result instead.
1 job for master in 74 minutes and 28 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #6552
test-all

01:14:28