If the stream is in an error state, returns the `GError` explaining that state.
Any type of error can be reported here depending on the implementation of the media stream.
A media stream in an error cannot be operated on, calls like [[email protected]] or [[email protected]] will not have any effect.
`GtkMediaStream` itself does not provide a way to unset an error, but implementations may provide options. For example, a [ [email protected]] will unset errors when a new source is set, e.g. with [[email protected]_file].
this |
a `GtkMediaStream` |
null if not in an error state or the `GError` of the stream |