comctl32: Do not send WM_NOTIFY if selecting an already-selected item.

dlls/comctl32/tests/treeview.c

@@ -1773,7 +1773,7 @@ static void test_TVS_SINGLEEXPAND(void)
         { &golf,     parent_singleexpand_seq5,  TRUE },
         { &hotel,    parent_singleexpand_seq6,  FALSE },
         { &india,    parent_singleexpand_seq7,  FALSE },
-        { &india,    empty_seq,  TRUE }
+        { &india,    empty_seq,  FALSE }
     };
 
     hTree = create_treeview_control(0);

dlls/comctl32/treeview.c

@@ -4475,6 +4475,9 @@ TREEVIEW_SelectItem(TREEVIEW_INFO *infoPtr, INT wParam, HTREEITEM item)
     if (item && !TREEVIEW_ValidItem(infoPtr, item))
 	return FALSE;
 
+    if (item == infoPtr->selectedItem)
+	return TRUE;
+
     TRACE("%p (%s) %d\n", item, TREEVIEW_ItemName(item), wParam);
 
     if (!TREEVIEW_DoSelectItem(infoPtr, wParam, item, TVC_UNKNOWN))