don't index outside of the path (closes #22312)
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 78af18c..7b5f7bb 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -50,6 +50,7 @@
         # Issue #19911: UNC part containing U+0130
         self.assertEqual(ntpath.splitdrive(u'//conky/MOUNTPOİNT/foo/bar'),
                          (u'//conky/MOUNTPOİNT', '/foo/bar'))
+        self.assertEqual(ntpath.splitdrive("//"), ("", "//"))
 
     def test_splitunc(self):
         tester('ntpath.splitunc("c:\\foo\\bar")',