I am creating model that merges all polygon feature classes into one feature class. I am using feature class iterator to feed collect value tool list. When dataset has polygons it work fine. But when there is no polygons in dataset it always retrieve one invalid record as "gdb/Dataset/FeatureClass". Of course gdb url and dataset and correct, except that FeatureClass is not valid. So when I get the list and try to merge this list it throws error of invalid parameter. How can I avoid adding this record to my list?