Plugin destruction causes crash due to problems with OpenGL destruction

[ThomasKroes]

void ScatterplotWidget::cleanup()
{
    qDebug() << "Deleting scatterplot widget, performing clean up...";
    _isInitialized = false;

    makeCurrent();
    _pointRenderer.destroy();
    _densityRenderer.destroy();
}

void PointArrayObject::destroy()
{
    glDeleteVertexArrays(1, &_handle); // Crashes right here
    _positionBuffer.destroy();
}