wxGUI/vdigit: fix syntax

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@49840 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/vdigit/wxdisplay.py

@@ -718,7 +718,7 @@ class DisplayDriver:
             self._drawSelected = False
         
         if layer > 0:
-            selected.field = layer
+            self.selected['field'] = layer
             self.selected['cats'] = ids
         else:
             field = -1