On sigwaitinfo or reading from a signalfd, signal processing sets up
signal handling via sigdelayed even if the handler address is NULL.
This doesn't have any impact on sigwaitinfo scenarios (or at least, I
wasn't able to come up with a reproducer) but it breaks signalfd
scenarios, where eventually a call to call_signal_handler from
sigdelayed will try to call the NULL function.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
92115a83a4