Well, there might be app_event msg without msg content.
Well, there might be app_event msg without msg content.

Do not log it in that case.

fixes #1174

ardadouk/omf6,ardadouk/omf6,phelipealves/omf,mytestbed/omf,phelipealves/omf,phelipealves/omf,mytestbed/omf,LABORA-UFG/omf,mytestbed/omf,LABORA-UFG/omf,mytestbed/omf,LABORA-UFG/omf,phelipealves/omf,LABORA-UFG/omf