fixed userid retrieval when empty set

main.py

@@ -88,7 +88,7 @@ def post_gateways():
         # TODO sanitize name, it must be a FQDN
 
         used_gateway_subids = []
-        for row in cu.execute('SELECT g.subid, u.id FROM gateway AS g INNER JOIN user AS u ON g.user = u.id WHERE u.name = ?', [str(user,)]):
+        for row in cu.execute('SELECT g.subid, u.id FROM user AS u LEFT JOIN gateway AS g ON g.user = u.id WHERE u.name = ?', [str(user,)]):
             used_gateway_subids.append(row[0])
             userid = row[1]