Bug 763961.

* src/client/application/geary-application.vala
  (GearyApplication::present): Always call show_all on the main window
  since if started hidden, it won't have had that called on it.

* src/client/application/geary-controller.vala:
  (GearyController::on_indicator_activated_application,
   GearyController::on_indicator_activated_composer,
   GearyController::on_indicator_activated_inbox): Always call show_all
  on the main window since if started hidden, it won't have had that
  called on it.