Delete _ImageViewer when delete DicomImageView, free memory

src/src/view/dicomimageview.cpp

@@ -69,6 +69,10 @@ DicomImageView::DicomImageView(QWidget* parent)
 //-----------------------------------------------------------------------------
 DicomImageView::~DicomImageView()
 {
+    if (_ImageViewer){
+        _ImageViewer->Delete();
+        _ImageViewer = nullptr;
+    }
 	_thread.quit();//event loop
 	_thread.wait(); //wait until return,block mode
 	_vcr_toolbar->deleteLater();