purge fields instead of setting to NULL as suggested by Florian

src/json/json.c

@@ -206,16 +206,8 @@ forget (const json_t *in)
             json_object_get (rx,
                              key)) )
       {
-        if (0 !=
+        (void) json_object_del (ret,
-            json_object_set_new (ret,
+                                key);
-                                 key,
-                                 json_null ()))
-        {
-          GNUNET_break (0);
-          json_decref (ret);
-          json_decref (rx);
-          return NULL;
-        }
         continue; /* already forgotten earlier */
       }
       t = forget (value);
@@ -281,16 +273,6 @@ forget (const json_t *in)
           json_decref (rx);
           return NULL;
         }
-        if (0 !=
-            json_object_set_new (ret,
-                                 key,
-                                 json_null ()))
-        {
-          GNUNET_break (0);
-          json_decref (ret);
-          json_decref (rx);
-          return NULL;
-        }
       }
       else
       {

src/json/test_json.c

@@ -178,7 +178,7 @@ test_contract (void)
                                              sizeof (h1));
     if (0 !=
         strcmp (s,
-                "287VXK8T6PXKD05W8Y94QJNEFCMRXBC9S7KNKTWGH2G2J2D7RYKPSHNH1HG9NT1K2HRHGC67W6QM6GEC4BSN1DPNEBCS0AVDT2DBP5G"))
+                "48YVST0SZJXWNG3KAD14SSK3AD0T5V01W5AE6E76DYKMJSC5BQ19M0FZ7CZP5JY26FC4AFXTXRGEVSQ1NSKPQ1DQ4GS9C4SAECG5RZ8"))
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Invalid reference hash: %s\n",