More fixes to potentially uninitialized shield_hit_infos.

git-svn-id: svn://svn.icculus.org/fs2open@10168 387891d4-d844-0410-90c0-e4c51a9137d3
Trunk sync r10168.

git-svn-id: svn://svn.icculus.org/fs2open@10169 387891d4-d844-0410-90c0-e4c51a9137d3