bpo-15303: Support widgets with boolean value False in Tkinter (GH-23904)
Use `widget is None` instead of checking the boolean value of a widget.
diff --git a/Lib/tkinter/ttk.py b/Lib/tkinter/ttk.py
index ab7aeb1..b854235 100644
--- a/Lib/tkinter/ttk.py
+++ b/Lib/tkinter/ttk.py
@@ -569,7 +569,7 @@ def instate(self, statespec, callback=None, *args, **kw):
matches statespec. statespec is expected to be a sequence."""
ret = self.tk.getboolean(
self.tk.call(self._w, "instate", ' '.join(statespec)))
- if ret and callback:
+ if ret and callback is not None:
return callback(*args, **kw)
return ret