make warning messages friendlier

git-svn-id: svn://svn.icculus.org/fs2open@10202 387891d4-d844-0410-90c0-e4c51a9137d3
don't freak out if we don't have a beam texture

git-svn-id: svn://svn.icculus.org/fs2open@10203 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Mantis 2896: AddressSanitizer: global-buffer-overflow in hud_lock_reset() hudlock.cpp (v2)

git-svn-id: svn://svn.icculus.org/fs2open@10204 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Mantis 2975: AddressSanitizer: global-buffer-overflow in HudGaugeLeadSight::render()

git-svn-id: svn://svn.icculus.org/fs2open@10205 387891d4-d844-0410-90c0-e4c51a9137d3