fix(jwt): Fixes when feature is missing.

There are cases where features is initialized with empty table, so we need to take into account that the key is missing in the table.

resources/prosody-plugins/util.lib.lua

@@ -255,9 +255,9 @@ end
 -- If features are missing but we have granted_features check that
 -- if features are missing from the token we check whether it is moderator
 function is_feature_allowed(ft, features, granted_features, is_moderator)
-    if features then
+    if features and features[ft] ~= nil then
         return features[ft] == "true" or features[ft] == true;
-    elseif granted_features then
+    elseif granted_features and granted_features[ft] ~= nil then
         return granted_features[ft] == "true" or granted_features[ft] == true;
     else
         return is_moderator;