skins2: better cleanup for button and checkbox

modules/gui/skins2/controls/ctrl_button.cpp

@@ -79,6 +79,11 @@ CtrlButton::CtrlButton( intf_thread_t *pIntf, const GenericBitmap &rBmpUp,
 
 CtrlButton::~CtrlButton()
 {
+    if( m_pImg )
+    {
+        m_pImg->stopAnim();
+        m_pImg->delObserver( this );
+    }
 }
 
 void CtrlButton::setLayout( GenericLayout *pLayout,

modules/gui/skins2/controls/ctrl_checkbox.cpp

@@ -111,6 +111,11 @@ CtrlCheckbox::CtrlCheckbox( intf_thread_t *pIntf,
 
 CtrlCheckbox::~CtrlCheckbox()
 {
+    if( m_pImgCurrent )
+    {
+        m_pImgCurrent->stopAnim();
+        m_pImgCurrent->delObserver( this );
+    }
     m_rVariable.delObserver( this );
 }