...after 7764439f "WidgetDefinition: add
'action' state for the PushButton" introduced code that downcasts that
suspicious ImplControlValue to a PushButtonValue

Change-Id: I3ed24cc4a862d53ad5b6e95b4707bab7947ce7ba
Reviewed-on: https://gerrit.libreoffice.org/71998Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Jenkins