opennds: fix a segfault caused that can be triggered via a bad url parameter

Fixes: WIFI-6724
Signed-off-by: John Crispin <john@phrozen.org>

feeds/ucentral/opennds/patches/200-exploits.patch

@@ -0,0 +1,13 @@
+Index: openNDS-9.0.0/src/http_microhttpd.c
+===================================================================
+--- openNDS-9.0.0.orig/src/http_microhttpd.c
++++ openNDS-9.0.0/src/http_microhttpd.c
+@@ -531,7 +531,7 @@ static int try_to_authenticate(struct MH
+ 		debug(LOG_DEBUG, "client->token=%s tok=%s ", client->token, tok );
+ 
+ 		//Check if token (tok) or hash_id (hid) mode
+-		if (strlen(tok) > 8) {
++		if (tok && strlen(tok) > 8) {
+ 			// hid mode
+ 			hash_str(hid, sizeof(hid), client->token);
+ 			safe_asprintf(&rhidraw, "%s%s", hid, config->fas_key);