gluon-mesh-vpn-core: fix two more missing NULL checks

read_stdout can return NULL and thus the return value need to be checked
prior to accessing it.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 344f8a47)

package/gluon-mesh-vpn-core/src/respondd.c

@@ -110,6 +110,9 @@ static struct json_object * get_mesh_vpn_enabled() {
 	int enabled = -1;
 	char *line = read_stdout("exec lua -e 'print(require(\"gluon.mesh-vpn\").enabled())'");
 
+	if (!line)
+		return NULL;
+
 	if (!strcmp(line, "true"))
 		enabled = 1;
 	if (!strcmp(line, "false"))
@@ -126,7 +129,7 @@ static struct json_object * get_mesh_vpn_enabled() {
 static struct json_object * get_active_vpn_provider() {
 	char *line = read_stdout("exec lua -e 'name, _ = require(\"gluon.mesh-vpn\").get_active_provider(); print(name)'");
 
-	if (!strcmp(line, "nil")) {
+	if (line && !strcmp(line, "nil")) {
 		free(line);
 		return NULL;
 	}