Created attachment 7476 
patch ensures stale data is cleared

The "Metadata" signal handler does not release player->artist (or player->title)
if the xesam:artists (or xesam:title) field is not present.

For example, if the player changes track from one with artist "FOO" to a resource
with no artist (e.g., an unbounded stream, like internet radio) the plugin still shows
"FOO" as the artist rather than an empty field.