wxGUI: fix UpdateMapsets()

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@46598 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/gis_set.py

@@ -599,7 +599,7 @@ class GRASSStartup(wx.Frame):
                                   location = locationName,
                                   gisdbase = self.gisdbase)
             
-            if not ret:
+            if ret == '':
                 raise gcmd.GError(_("No mapsets available in location <%s>") % locationName)
             
             for line in ret.splitlines():