Fix cover not rendered for same track b/w sessions

There was a bug where the current track if stopped in between the
playback and resumed didn't refresh the cover art (not rendered). This
was happening because of the ctrackID being the same between the
sessions. This commit fixes that.

ui/progress.go

@@ -85,6 +85,12 @@ func RefreshProgress(force bool) {
 		return
 	}
 	state = s
+
+	// Reset the "cached" if nothing is playing (TODO: better name)[
+	if s.Item == nil {
+		ctrackId = ""
+	}
+
 	if coverArt != nil {
 		// If No Item is playing
 		if (state.Item == nil) ||