notify: don't close FD 0

This fixes a regression where closing a terminal instance, or hard- or
soft-resetting a terminal caused FD 0 to be closed.

This meant it became re-usable. Usually, by memfd_create() when
allocating a new surface buffer. So far nothing _really_ bad has
happened.

But what if FD 0 is now used by a memfd, and we close _another_
terminal instance?

This causes our memfd to be closed. And then, when e.g. trying to
scroll the terminal content: fallocate() fails with bad FD.

terminal.c

@@ -1330,6 +1330,10 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
         }
     }
 
+    for (size_t i = 0; i < ALEN(term->notification_icons); i++) {
+        term->notification_icons[i].tmp_file_fd = -1;
+    }
+
     add_utmp_record(conf, reaper, ptmx);
 
     if (!pty_path) {