fix: Fix the bug that the parameter default of tkinter.Wm.iconbitmap could not take effect when passing an empty string

Author: Xiaokang2022

Lib/tkinter/__init__.py

@@ -2265,7 +2265,7 @@ def wm_iconbitmap(self, bitmap=None, default=None):
         explicitly.  DEFAULT can be the relative path to a .ico file
         (example: root.iconbitmap(default='myicon.ico') ).  See Tk
         documentation for more information."""
-        if default:
+        if default is not None:
             return self.tk.call('wm', 'iconbitmap', self._w, '-default', default)
         else:
             return self.tk.call('wm', 'iconbitmap', self._w, bitmap)