Not promoting a mouse-up event to a click event when it was prevented by a mouse capture. See #752

application.go

@@ -460,8 +460,8 @@ func (a *Application) fireMouseActions(event *tcell.EventMouse) (consumed, isMou
 			if buttons&buttonEvent.button != 0 {
 				fire(buttonEvent.down)
 			} else {
-				fire(buttonEvent.up)
-				if !clickMoved {
+				fire(buttonEvent.up) // A user override might set event to nil.
+				if !clickMoved && event != nil {
 					if a.lastMouseClick.Add(DoubleClickInterval).Before(time.Now()) {
 						fire(buttonEvent.click)
 						a.lastMouseClick = time.Now()