Avoid self-assignment causing wrong drop, found by CuteAlien.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2185 dfc29bdd-3216-0410-991c-e03cc46cb475

include/ISceneNode.h

@@ -590,12 +590,15 @@ namespace scene
 		\param selector New triangle selector for this scene node. */
 		virtual void setTriangleSelector(ITriangleSelector* selector)
 		{
-			if (TriangleSelector)
-				TriangleSelector->drop();
+			if (TriangleSelector != selector)
+			{
+				if (TriangleSelector)
+					TriangleSelector->drop();
 
-			TriangleSelector = selector;
-			if (TriangleSelector)
-				TriangleSelector->grab();
+				TriangleSelector = selector;
+				if (TriangleSelector)
+					TriangleSelector->grab();
+			}
 		}