Remove EVT_ERASE_BACKGROUND events - pretty sure these were there for older versions of wx where the background wasn't erased properly

gui/mainFrame.py

@@ -102,14 +102,10 @@ class PFPanel(wx.Panel):
     def __init__(self, parent):
         wx.Panel.__init__(self, parent)
         self.Bind(wx.EVT_PAINT, self.OnPaint)
-        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnBkErase)
 
     def OnPaint(self, event):
         event.Skip()
 
-    def OnBkErase(self, event):
-        pass
-
 
 class OpenFitsThread(threading.Thread):
     def __init__(self, fits, callback):