Fix a couple of (AFAICS false) may-be-used-uninitialized warnings that show up with gcc 4.8.3.

Change-Id: I71c9013670dd6e8c74e039bd252cfac2c9e95a18
Reviewed-on: https://code.wireshark.org/review/5246
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>