MediaSet: Do not show an error if any object does not have children
MediaSet: Do not show an error if any object does not have children

Change-Id: I24cb98ba17ef113fe0c1938a7d2ed0ad49ff112a

ESTOS/kms-core,ESTOS/kms-core,Kurento/kms-core,ESTOS/kms-core,Kurento/kms-core,Kurento/kms-core,ESTOS/kms-core,Kurento/kms-core