fix uninitialized member SwipeTriggerUpdateEvent::m_sender

Author: taj-ny

src/libinputactions/triggers/SwipeTrigger.h

@@ -56,7 +56,7 @@ class SwipeTriggerUpdateEvent : public MotionTriggerUpdateEvent
 private:
     qreal m_angle{};
     qreal m_averageAngle{};
-    const InputDevice *m_sender;
+    const InputDevice *m_sender{};
 };
 
 /**