fTools: fix error basic statistics

Author: jef-n

python/plugins/fTools/tools/doVisual.py

@@ -91,8 +91,8 @@ def update( self ):
         else:
           self.useSelected.setCheckState( Qt.Unchecked )
       # add all fields in combobox because now we can work with text fields too
-      for i in changedField:
-        self.cmbField.addItem( unicode( changedField[i].name() ) )
+      for f in changedField:
+        self.cmbField.addItem( unicode( f.name() ) )
 
   def accept( self ):
     if self.inShape.currentText() == "":