don't return null objects from recursive iterators
don't return null objects from recursive iterators

TitoAgudelo/tangram,tangrams/tangram,DHaylock/tangram,rosamcgee/tangram,DHaylock/tangram,rosamcgee/tangram,xvilan/tangram,zerebubuth/tangram,ceseale/tangram,tangrams/tangram,TitoAgudelo/tangram,ceseale/tangram,xvilan/tangram,TitoAgudelo/tangram,ceseale/tangram,rosamcgee/tangram,DHaylock/tangram,taylorhxu/tangram,taylorhxu/tangram,zerebubuth/tangram,xvilan/tangram,zerebubuth/tangram,taylorhxu/tangram