gh-103685: Fix tkinter.Menu.index() for Tk 8.7

Lib/test/test_tkinter/test_widgets.py

@@ -1377,6 +1377,11 @@ class MenuTest(AbstractWidgetTest, unittest.TestCase):
     def create(self, **kwargs):
         return tkinter.Menu(self.root, **kwargs)
 
+    def test_indexcommand_none(self):
+        widget = self.create()
+        i = widget.index('none')
+        self.assertIsNone(i)
+
     def test_configure_postcommand(self):
         widget = self.create()
         self.checkCommandParam(widget, 'postcommand')

Lib/tkinter/__init__.py

@@ -3430,8 +3430,7 @@ def entryconfigure(self, index, cnf=None, **kw):
     def index(self, index):
         """Return the index of a menu item identified by INDEX."""
         i = self.tk.call(self._w, 'index', index)
-        if i == 'none': return None
-        return self.tk.getint(i)
+        return None if i in ('', 'none') else self.tk.getint(i)  # GH-103685.
 
     def invoke(self, index):
         """Invoke a menu item identified by INDEX and execute

Misc/NEWS.d/next/Library/2023-04-24-00-34-23.gh-issue-103685.U14jBM.rst

@@ -0,0 +1 @@
+Prepare :meth:`tkinter.Menu.index` for Tk 8.7 so that it does not raise ``TclError: expected integer but got ""`` when it should return ``None``.