When we are adding property group and if we left all fields blank then also it the property group is getting added for that particular file or folder. I can show an error if the fields are empty but I am not able to prevent the property group from getting added. Can you please tell me what code to add and in which file it is to be added?
Setting property groups goes with two steps. First add groups ( which adds all fields with blank value ) and second setting properties ( what also could be set blank ).
Take a look at the end of this wiki section about force setting properties, http://wiki.openkm.com/index.php/Form_E ... escription
In you case I suggest think do some report to looking for empty fields ( add group and not set property group case ). Normally this is the right way to solve your problem.