title: How to solve the "GLib-GObject-CRITICAL g_object_unref: assertion 'G_IS_OBJECT (object)' failed" error?
body: <p>I have developed a simple application (using QT) to record the video from laptop's camera. I've used the following classes:</p>
  
  <pre><code> QCamera
   QCameraInfo
   QMediaRecorder
   QUrl
   QCameraViewfinder
   QCameraImageCapture
  </code></pre>
  
  <p>It works and it can show the video and I am able to still an image but, when I try to record a video using "QMediaRecorder" I face the following error:</p>
  
  <p>Error message:</p>
  
  <blockquote>
    <p>(videoD:19102): GLib-GObject-CRITICAL **: 13:01:07.717: g_object_unref: assertion 'G_IS_OBJECT (object)' failed</p>
  </blockquote>
  
  <p>The operation system is Ubuntu 18 and I have installed libpulse-dev.</p>