Fix for Mantis 3064 from MageKing17: Followup fix.

git-svn-id: svn://svn.icculus.org/fs2open@10928 387891d4-d844-0410-90c0-e4c51a9137d3
Fix gcc warning in hud/hud.cpp

the address of ‘Hud_text_flash’ will always evaluate as ‘true’ [-Waddress]

git-svn-id: svn://svn.icculus.org/fs2open@10929 387891d4-d844-0410-90c0-e4c51a9137d3