[Nel] Fix for snowballs2 animation.cpp

[Sebastian]

Animations weren't working for snowballs2, and left-clicking
(throwing) caused the game to crash with this error:

----------------------------------------------------------------------------
snowballs.exe AST  2704 animation.cpp 189 : "!entity.Instance.empty()
&& !entity.Skeleton.empty() && AnimationSet != NULL"
----------------------------------------------------------------------------

I tracked this down to a typo on line 165 in animation.cpp:
---------------------------------------------------------------------------
if (!entity.Skeleton.empty())
return;
---------------------------------------------------------------------------
should be:
---------------------------------------------------------------------------
if (entity.Skeleton.empty())
return;
--------------------------------------------------------------------------

This fix allowed animations to work in snowballs2.  Now the game runs
perfectly for me.

-Sebastian