playlist/Print: don't skip non-existent songs in "listplaylist"

Skipping those songs silently will confuse the client, because
commands specifying the song index within a playlist
(e.g. playlistdelete) will be out of sync.

This copies spl_print()'s behavior to playlist_file_print().

NEWS

@@ -1,4 +1,6 @@
 ver 0.19.7 (not yet released)
+* playlist
+  - don't skip non-existent songs in "listplaylist"
 
 ver 0.19.6 (2014/12/08)
 * decoder

src/playlist/Print.cxx

@@ -43,12 +43,13 @@ playlist_provider_print(Client &client, const char *uri,
 	DetachedSong *song;
 	while ((song = e.NextSong()) != nullptr) {
 		if (playlist_check_translate_song(*song, base_uri.c_str(),
-						  loader)) {
+						  loader) &&
-			if (detail)
+		    detail)
-				song_print_info(client, *song);
+			song_print_info(client, *song);
-			else
+		else
-				song_print_uri(client, *song);
+			/* fallback if no detail was requested or no
-		}
+			   detail was available */
+			song_print_uri(client, *song);
 
 		delete song;
 	}