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

@@ -589,6 +589,8 @@ namespace scene
 		ISceneNode::getTriangleSelector().
 		\param selector New triangle selector for this scene node. */
 		virtual void setTriangleSelector(ITriangleSelector* selector)
+		{
+			if (TriangleSelector != selector)
 			{
 				if (TriangleSelector)
 					TriangleSelector->drop();
@@ -597,6 +599,7 @@ namespace scene
 				if (TriangleSelector)
 					TriangleSelector->grab();
 			}
+		}
 
 
 		//! Updates the absolute position based on the relative and the parents position