input: intercept ^Z also when --minibar is active

For some reason, calling halfdelay() undoes the ISIG mask.
So, mask keyboard interrupts again immediately after the call.

Reported-by: Peter Passchier <peter@passchier.net>

src/winio.c

@@ -189,6 +189,7 @@ void read_keys_from(WINDOW *win)
 					lastmessage > VACUUM && lastmessage < ALERT) {
 		timed = TRUE;
 		halfdelay(8);
+		disable_kb_interrupt();
 	}
 #endif