WCCP: Remove uneeded check (pinfo & info_tree)

Remove also some false positive Dereference of null pointer

Change-Id: I09687993531827c6e4f5178f3414ddd9a2702038
Reviewed-on: https://code.wireshark.org/review/5506
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Evan Huus <eapache@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>