Merge pull request #757 from tjhowse/Fix_Screen_init

Initialise Screen if SetScreen called before Run

application.go

@@ -181,6 +181,7 @@ func (a *Application) SetScreen(screen tcell.Screen) *Application {
 		// Run() has not been called yet.
 		a.screen = screen
 		a.Unlock()
+		screen.Init()
 		return a
 	}