Fix Coverity 1093619 Array compared against 0 in delete_player()

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@11004 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Coverity 1093621 Array compared against 0 in send_accept_packet()

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@11005 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Coverity 1093622 Array compared against 0 in process_new_player_packet()

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@11006 387891d4-d844-0410-90c0-e4c51a9137d3