Add a check to appendToTable to catch illegal input, and fix a test
case triggering this check.
Also removing unused variables and fix indentation.

R=ahaas@chromium.org

Change-Id: I0eaa48ab95ef710530a3cfbe94ed4dd419618cda
Reviewed-on: https://chromium-review.googlesource.com/458436
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44027}