fixed a severe bug with pointer_color state tracking (no longer checks .colorarray...

fixed a severe bug with pointer_color state tracking (no longer checks .colorarray, so you don't have to do the GL_Color/GL_UseColorArray call before R_Mesh_State anymore), this fixes explosion coloring when using pointer_color for other stuff rendered immediately before it
fixed a crash when entire sequentialchain is emptied while trying to get space for a new cache item (this happened!  I can't guess why though)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@3029 d7cf8633-e32d-0410-b094-e92efae38249