filter out undefined fields

test/index.js

@@ -188,3 +188,28 @@ test ('recursive filter multifield', (t) => {
   const result = util.recursive_filter (raw, [ filter ]);
   t.deepEqual (filtered, result);
 });
+
+test ('recursive filter multifield input error', (t) => {
+  t.notThrows (() => {
+    util.recursive_filter (
+      [ { foo: 'bar' } ],
+      [ { fields: '', field: 'foo', filter: /a/u } ]
+    );
+  });
+});
+
+test ('recursive filter undefined multifield', (t) => {
+  const res = util.recursive_filter (
+    [ { foo: 'bar' } ],
+    [
+      {
+        fields: [
+          'foo',
+          'bar'
+        ],
+        filter: /\s/u
+      }
+    ]
+  );
+  t.deepEqual (res, []);
+});