Destroying assets is not permitted to avoid data loss.

Hi i read some previous threads but i don't understand what im doing wrong. So if I understood correctly i have to Destory a clone of prefab not prefab by itself . This is my code:

Code (CSharp):

1.     public void ChoseBuildingFromUI(int id)
2.     {
3.         Debug.Log(id);
4.  
5.         if(chosed_Building != null)
6.         {
7.             RemoveObjectFromGame();
8.         }
9.  
10.         GameObject objectToBuild =(GameObject)Instantiate(buildings_all[id], Vector3.zero, Quaternion.identity);
11.  
12.         chosed_Building = objectToBuild;
13.         chosed_building_rigid = chosed_Building.GetComponent<Rigidbody>();
14.      
15.  
16.         Debug.Log("You've chosed building :" + buildings_all[id].name);
17.     }
18.  
19.     public void  RemoveObjectFromGame()
20.     {
21.         chosed_building_rigid = null;
22.         Destroy(chosed_Building);
23.         chosed_Building = null;
24.     }
25.  

So My chosed_Building = Cube(Clone) but still i get warning
"
Destroying assets is not permitted to avoid data loss.
If you really want to remove an asset use DestroyImmediate (theObject, true);
UnityEngine.Objectestroy(Object)
BuildMenu:RemoveObjectFromGame() (at Assets/Scripts/Modes/BuildMenu/BuildMenu.cs:94)
BuildMenu:ChoseBuildingFromUI(Int32) (at Assets/Scripts/Modes/BuildMenu/BuildMenu.cs:79)
<>c__DisplayClass12_0:<AddListenerToButton>b__0() (at Assets/Scripts/Modes/BuildMenu/BuildMenu.cs:69)
UnityEngine.EventSystems.EventSystem:Update()"

chosed_Building is public GameObject


// It looks like i had one line in another script which after Input.GetMouseButtonUp(0) put again Cube(Clone) as chosed_building. So for now i fixed my problem Thread can be closed sorry.