- SW: clear old user content before allocating a new one.

If old data gets in here it may break the game.
https://github.com/coelckers/Raze/issues/349

source/games/sw/src/sprite.cpp

@@ -870,6 +870,7 @@ SpawnUser(short SpriteNum, short id, STATEp state)
 
     ASSERT(!Prediction);
 
+    User[SpriteNum].Clear();    // make sure to delete old, stale content first!
     User[SpriteNum].Alloc();
     u = User[SpriteNum].Data();