Seeking on pipeline with NULL clock fails assertion.

[Nate Bogdanowicz]

Hello,

When I create a pipeline and tell it to _use_clock(..., NULL) and
later call a flushing seek, I get a "GStreamer-CRITICAL **:
gst_object_ref: assertion `object != NULL' failed". Removing the
_use_clock() call eliminates this problem. Using gdb, I can see that
the problem comes when gst_pipeline_change_state() tries to
gst_object_ref(cur_clock) in gstpipeline.c:422 (in gstreamer 0.10.36).

Am I doing something wrong, or should I file this as a bug? I haven't
been able to find a matching existing bug. I've also made a simple
patch that does a null-check, which fixes the issue.

This problem also seems to exist in the 1.0 branch.

Thanks,
Nate Bogdanowicz