Adds DRAKE_ASSERT in get_input_force
Adds DRAKE_ASSERT in get_input_force

billhoffman/drake,sheim/drake,billhoffman/drake,billhoffman/drake,sheim/drake,sheim/drake,sheim/drake,billhoffman/drake,billhoffman/drake,billhoffman/drake,sheim/drake,sheim/drake,sheim/drake,sheim/drake,billhoffman/drake,billhoffman/drake