In my case, when trying to open the properties window in Nautilus over a .mp4 file or if I try to play this file with Totem, I am getting the same error:
"(nautilus:7717): GStreamer-CRITICAL **: gst_structure_new_empty: assertion 'gst_structure_validate_name (name)' failed
Segmentation fault (core dumped)"
In my case, when trying to open the properties window in Nautilus over a .mp4 file or if I try to play this file with Totem, I am getting the same error: new_empty: assertion 'gst_structure_ validate_ name (name)' failed
"(nautilus:7717): GStreamer-CRITICAL **: gst_structure_
Segmentation fault (core dumped)"
I can open the file with VLC though...