[NUI] If the view had focus when it was unparented, the focus is clea…

…red. (Samsung#4654)

When the view is unparented, the focus is not cleared.
So, when app re-add the view and SetCurrentFocusView, app do not receiving the FocusGained event.

src/Tizen.NUI/src/public/BaseComponents/ViewInternal.cs

@@ -1035,6 +1035,11 @@ internal IntPtr GetPtrfromView()
 
         internal void RemoveChild(View child)
         {
+            // If the view had focus, it clears focus.
+            if (child == FocusManager.Instance.GetCurrentFocusView())
+            {
+                FocusManager.Instance.ClearFocus();
+            }
             // Do actual child removal
             Interop.Actor.Remove(SwigCPtr, View.getCPtr(child));
             if (NDalicPINVOKE.SWIGPendingException.Pending)

src/Tizen.NUI/src/public/Common/Layer.cs

@@ -334,6 +334,12 @@ public override void Remove(View child)
                 Tizen.Log.Error("NUI", "You have deleted a view that is not a child of this layer.");
                 return;
             }
+            // If the view had focus, it clears focus.
+            if (child == FocusManager.Instance.GetCurrentFocusView())
+            {
+                FocusManager.Instance.ClearFocus();
+            }
+
             Interop.Actor.Remove(SwigCPtr, View.getCPtr(child));
             if (NDalicPINVOKE.SWIGPendingException.Pending)
                 throw NDalicPINVOKE.SWIGPendingException.Retrieve();