leak-795988: Correctly remove resize handler
leak-795988: Correctly remove resize handler

We were incorrectly removing an event handler that we hadn't added in
some situations. Whilst this didn't actually cause a memory leak, it
did confuse the event logging.

Signed-off-by: Joe Walker <7a17872fbb32c7d760c9a16ee3076daead11efcf@mozilla.com>

mozilla/gcli,mozilla/gcli,mozilla/gcli,joewalker/gcli,joewalker/gcli