only clean up openGL buffers if context is still valid

selfdrive/ui/qt/widgets/cameraview.cc

@@ -84,10 +84,12 @@ CameraViewWidget::CameraViewWidget(VisionStreamType stream_type, QWidget* parent
 
 CameraViewWidget::~CameraViewWidget() {
   makeCurrent();
-  doneCurrent();
+  if (isValid()) {
     glDeleteVertexArrays(1, &frame_vao);
     glDeleteBuffers(1, &frame_vbo);
     glDeleteBuffers(1, &frame_ibo);
+  }
+  doneCurrent();
 }
 
 void CameraViewWidget::initializeGL() {