LocateUri: migrate from class Error to C++ exceptions

src/queue/Playlist.hxx

@@ -209,12 +209,13 @@ public:
 	unsigned AppendSong(PlayerControl &pc, DetachedSong &&song);
 
 	/**
-	 * @return the new song id or 0 on error
+	 * Throws #std::runtime_error on error.
+	 *
+	 * @return the new song id
 	 */
 	unsigned AppendURI(PlayerControl &pc,
 			   const SongLoader &loader,
-			   const char *uri_utf8,
-			   Error &error);
+			   const char *uri_utf8);
 
 protected:
 	void DeleteInternal(PlayerControl &pc,

src/queue/PlaylistEdit.cxx

@@ -124,13 +124,9 @@ playlist::AppendSong(PlayerControl &pc, DetachedSong &&song)
 
 unsigned
 playlist::AppendURI(PlayerControl &pc, const SongLoader &loader,
-		    const char *uri,
-		    Error &error)
+		    const char *uri)
 {
-	std::unique_ptr<DetachedSong> song(loader.LoadSong(uri, error));
-	if (song == nullptr)
-		return 0;
-
+	std::unique_ptr<DetachedSong> song(loader.LoadSong(uri));
 	return AppendSong(pc, std::move(*song));
 }