Change deprecated _popupSettingsDialog() to popupSettingsDialog()

Author: NSoiffer

addon/globalPlugins/MathCAT/__init__.py

@@ -38,7 +38,7 @@ def add_MathCAT_menu(self):
             mainFrame.sysTrayIcon.Bind(wx.EVT_MENU, self.on_settings, self.settings)
 
     def on_settings(self, evt):
-        mainFrame._popupSettingsDialog(UserInterface)
+        mainFrame.popupSettingsDialog(UserInterface)
 
     def terminate(self):
         try: