show empty image if no map to display

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@42812 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/gui_modules/mapdisp_window.py

@@ -687,7 +687,7 @@ class BufferedWindow(MapWindow, wx.Window):
         @return wx.Image instance (map composition)
         """
         imgId = 99
-        if self.Map.mapfile and os.path.isfile(self.Map.mapfile) and \
+        if self.mapfile and self.Map.mapfile and os.path.isfile(self.Map.mapfile) and \
                 os.path.getsize(self.Map.mapfile):
             img = wx.Image(self.Map.mapfile, wx.BITMAP_TYPE_ANY)
         else: