Strange error (419576)

Unity Engine
1

i got this error:

InvalidOperationException: Operation is not valid due to the current state of the object
System.Collections.Stack.Pop ()
UnityEngine.GUIClip.Pop ()
UnityEngine.GUI.EndGroup ()
UserInterface+FPSTab$27+$.MoveNext () (at Assets\Scripts\Application\MainGame\GUI\UserInterface.js:132)

the warning fires when clicking a button which shows label that holds current fps

here is the code

function FPSTab(){

 GUI.BeginGroup(Rect(xFPSPosition,0,95,30));
 GUI.Label(Rect(10,5,40,25),FPS.returnFPS());
	
  if(GUI.Button(Rect(50,5,40,25),"FPS")){
       if(bFPSVisible){		
	var t = 0.0;
	while (t<1.0){
	   t+=Time.deltaTime *(1.0/0.5);		
	   xFPSPosition=Mathf.Lerp(xFPSPosition,-45.0,t);
	yield;
	}
			
					bFPSVisible=false;
	} else {
   	t = 0.0;
        while (t<1.0){
	
t+=Time.deltaTime *(1.0/0.5);		
xFPSPosition=Mathf.Lerp(xFPSPosition,0,t);
yield;
}
bFPSVisible=true;
			}
		}
 GUI.EndGroup();

}
2

Maybe it’s the yields?

3

yes it is, it complains if you call them from OnGUI