am 4532e0d6: am 933ccc85: Calculator: don\'t allow to enter an operator after an initial minus.

Merge commit '4532e0d631ce10cc944d92f212b29a9d2b72f3eb'

* commit '4532e0d631ce10cc944d92f212b29a9d2b72f3eb':
  Calculator: don't allow to enter an operator after an initial minus.