don't assert that metaroom backgrounds haven't already been added
don't assert that metaroom backgrounds haven't already been added

crystalline/openc2e,bdonlan/openc2e,crystalline/openc2e,ccdevnet/openc2e,ccdevnet/openc2e,ccdevnet/openc2e,bdonlan/openc2e,ccdevnet/openc2e,bdonlan/openc2e,ccdevnet/openc2e,crystalline/openc2e,ccdevnet/openc2e,crystalline/openc2e,bdonlan/openc2e,crystalline/openc2e