mgmt: respond Nack when query is invalid

refs #1993

Change-Id: I21e398cd7b2e562b7dc759a89f6e668960e72c41
diff --git a/daemon/mgmt/face-manager.cpp b/daemon/mgmt/face-manager.cpp
index daba08e..712d096 100644
--- a/daemon/mgmt/face-manager.cpp
+++ b/daemon/mgmt/face-manager.cpp
@@ -1158,7 +1158,7 @@
       !FACES_QUERY_DATASET_PREFIX.isPrefixOf(query))
     {
       NFD_LOG_DEBUG("query result: malformed");
-      //sendNack(query);
+      sendNack(query);
       return;
     }
 
@@ -1170,7 +1170,7 @@
   catch (tlv::Error&)
     {
       NFD_LOG_DEBUG("query result: malformed filter");
-      //sendNack(query);
+      sendNack(query);
       return;
     }