[2.7] bpo-33096: Fix ttk.Treeview.insert. (GH-6228) (GH-6326)

Allow ttk.Treeview.insert to insert iid that has a false boolean value.
Note iid=0 and iid=False would be same.
(cherry picked from commit 3ab44c0)

Co-authored-by: Garvit Khatri <garvitdelhi@gmail.com>

Lib/lib-tk/test/test_ttk/test_widgets.py

@@ -1485,6 +1485,15 @@ def test_insert_item(self):
             self.tv.insert('', 'end', text=value), text=None),
             value)
 
+        # test for values which are not None
+        itemid = self.tv.insert('', 'end', 0)
+        self.assertEqual(itemid, '0')
+        itemid = self.tv.insert('', 'end', 0.0)
+        self.assertEqual(itemid, '0.0')
+        # this is because False resolves to 0 and element with 0 iid is already present
+        self.assertRaises(tkinter.TclError, self.tv.insert, '', 'end', False)
+        self.assertRaises(tkinter.TclError, self.tv.insert, '', 'end', '')
+
 
     def test_selection(self):
         # item 'none' doesn't exist

Lib/lib-tk/ttk.py

@@ -1332,7 +1332,7 @@ def insert(self, parent, index, iid=None, **kw):
         already exist in the tree. Otherwise, a new unique identifier
         is generated."""
         opts = _format_optdict(kw)
-        if iid:
+        if iid is not None:
             res = self.tk.call(self._w, "insert", parent, index,
                 "-id", iid, *opts)
         else: