Revert "Cast result of rna_RenderSettings_use_game_engine_get to {0, 1}"

There are more flags that trigger this assertion, so I want to discuss
an appropriate way to fix it before changing them all.

This reverts commit b1191e5caf.

source/blender/makesrna/intern/rna_scene.c

@@ -1245,7 +1245,7 @@ static int rna_RenderSettings_use_game_engine_get(PointerRNA *ptr)
 
 	for (type = R_engines.first; type; type = type->next)
 		if (STREQ(type->idname, rd->engine))
-			return !!(type->flag & RE_GAME);
+			return (type->flag & RE_GAME);
 	
 	return 0;
 }