Correct xcatd behavior when serializing data to client incurred by XML formatting work change

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@9829 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

xCAT-server/sbin/xcatd

@@ -1396,6 +1396,7 @@ sub convey_response {
     build_response($resp);
     return;
   }
+  unless ($resp) { return; }
   $resp = freeze($resp);
   #$resp = XMLout($resp,KeyAttr=>[], NoAttr=>1,RootName=>'xcatresponse');
   #sanitize the response, to avoid being killed by non-printable bytes