bookmark-list: Fix memory leak
According to the documentation1, GFileMonitor object must be freed
when it is not necessary.
g_file_monitor_cancel() doesn't free the object.
Also, clean up code on do_finalize().
According to the documentation1, GFileMonitor object must be freed
when it is not necessary.
g_file_monitor_cancel() doesn't free the object.
Also, clean up code on do_finalize().