Added missing virtual destructor.

Libs/Widgets/ctkPushButton.cpp

@@ -39,6 +39,11 @@ ctkPushButtonPrivate::ctkPushButtonPrivate(ctkPushButton& object)
 }
 
 //-----------------------------------------------------------------------------
+ctkPushButtonPrivate::~ctkPushButtonPrivate()
+{
+}
+
+//-----------------------------------------------------------------------------
 void ctkPushButtonPrivate::init()
 {
 }

Libs/Widgets/ctkPushButton_p.h

@@ -28,6 +28,9 @@ class ctkPushButtonPrivate
 protected:
   ctkPushButton* const q_ptr;
 public:
+
+  virtual ~ctkPushButtonPrivate();
+
   ctkPushButtonPrivate(ctkPushButton& object);
   void init();