rubber band detaching committed previously should only happen when attached to track, not karts

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/trunk/supertuxkart@2783 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/items/rubber_band.cpp

@@ -137,7 +137,7 @@ void RubberBand::update(float dt)
         Vec3 diff   = p-k;
         
         // detach rubber band if kart gets very close to hit point
-        if(diff.length2() < 10*10)
+        if(m_attached_state==RB_TO_TRACK && diff.length2() < 10*10)
         {
             // Rubber band snaps
             m_plunger->hit(NULL);