fix backspace and delete not working in FloatEdit fields

grocery_transactions.py

@@ -200,7 +200,7 @@ class AutoCompleteFloatEdit(numedit.FloatEdit):
         elif key in ('=', 'enter',):
             self.calc()
             return
-        elif key in ('esc', 'left', 'right', 'up', 'down',) or \
+        elif key in ('esc', 'left', 'right', 'up', 'down', 'backspace', 'delete',) or \
              key in '0123456789.':
             return super(AutoCompleteFloatEdit, self).keypress(size, key)
         else: