Check hapd_iface more consistently in hostapd_disable_iface()

There is no point in the hapd_iface == NULL validate after this pointer
has been dereferences, so move the code dereferencing hapd_iface after
the check.

Signed-hostap: Jouni Malinen <j@w1.fi>

src/ap/hostapd.c

@@ -1113,12 +1113,13 @@ int hostapd_reload_iface(struct hostapd_iface *hapd_iface)
 int hostapd_disable_iface(struct hostapd_iface *hapd_iface)
 {
 	size_t j;
-	struct hostapd_bss_config *bss = hapd_iface->bss[0]->conf;
+	struct hostapd_bss_config *bss;
 	const struct wpa_driver_ops *driver;
 	void *drv_priv;
 
 	if (hapd_iface == NULL)
 		return -1;
+	bss = hapd_iface->bss[0]->conf;
 	driver = hapd_iface->bss[0]->driver;
 	drv_priv = hapd_iface->bss[0]->drv_priv;