hostapd: fix crash regression triggered by mesh mode

Fixes: 60fb4c92b6 ("hostapd: add ubus reload")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
[daniel@makrotopia.org: polish commit message]

package/network/services/hostapd/patches/700-wifi-reload.patch

@@ -87,7 +87,7 @@
  	hapd->iconf = conf;
  	hapd->conf = bss;
  	hapd->iface = hapd_iface;
-+	if (bss->config_id)
++	if (bss && bss->config_id)
 +		hapd->config_id = strdup(bss->config_id);
 +	else
 +		hapd->config_id = NULL;