imageoverlay: Not draw a circle if an overlay image is not defined
imageoverlay: Not draw a circle if an overlay image is not defined

Change-Id: I8f5e9ada5bddec95362269cb3a19a94e18cdaccb

Kurento/kms-elements,TribeMedia/kms-elements,TribeMedia/kms-elements,Kurento/kms-elements,shelsonjava/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements