Attempt to reload stream on "Server does not support seeking." error (#5923)

When the network connection changes while playing an HTTP stream, I always get the "Server does not support seeking." error from GStreamer.
It seems like GStreamer tries to seek on reconnect, which fails, an propagates the error to Clementine which in turn ceases playback with
the error message handed through from GStreamer, even though there is now a perfectly fine network connection again.

As a workaround, try to reload the stream when this error occurs.

fixes #5116

src/engines/gstengine.cpp

@@ -692,6 +692,18 @@ void GstEngine::HandlePipelineError(int pipeline_id, const QString& message,
 
   qLog(Warning) << "Gstreamer error:" << message;
 
+  // try to reload the URL in case of a drop of the connection
+  if (domain == GST_RESOURCE_ERROR && error_code == GST_RESOURCE_ERROR_SEEK) {
+    if (Load(url_, 0, false, 0, 0)) {
+
+      current_pipeline_->SetState(GST_STATE_PLAYING);
+
+      return;
+    }
+
+    qLog(Warning) << "Attempt to reload " << url_ << " failed";
+  }
+
   current_pipeline_.reset();
 
   BufferingFinished();