Squelch some compiler warnings.

Change-Id: Ie39c7b0c1fef8f862cec016a3a1a5bd1451a3df2
Reviewed-on: https://code.wireshark.org/review/2905
Reviewed-by: Guy Harris <guy@alum.mit.edu>
(cherry picked from commit 79fcc6a1a36e0637ce21f65a7e27bc6d90213509)
Reviewed-on: https://code.wireshark.org/review/2926