plugins: Properties: Add 'Last Modified' for audio files

In commit f3358eb, the Properties plugin started using the
Track Info screen for audio files, which didn't show when
the file was last modified. This adds it back.

Change-Id: I3ce519da234a4bcadab1d64b67de0298cada8f6e

apps/gui/wps.c

@@ -1035,7 +1035,7 @@ long gui_wps_show(void)
                 gwps_leave_wps(true);
                 if (browse_id3(audio_current_track(),
                         playlist_get_display_index(),
-                        playlist_amount()))
+                        playlist_amount(), NULL))
                     return GO_TO_ROOT;
                 restore = true;
             }