Initialize the attributes of IfcLateBoundEntity to NULL upon construction.

Make sure IfcWritableEntity does not return null pointers, since getArgumentCount() is unreliable for instances being created from keyword arguments in Python.

src/ifcparse/IfcLateBoundEntity.cpp

@@ -48,6 +48,10 @@ IfcParse::IfcLateBoundEntity::IfcLateBoundEntity(const std::string& s) {
 	for (std::string::iterator i = S.begin(); i != S.end(); ++i ) *i = toupper(*i);
 	_type = IfcSchema::Type::FromString(S);
 	entity = new IfcWrite::IfcWritableEntity(_type);
+	for (unsigned i = 0; i < getArgumentCount(); ++i) {
+		// Side effect of this is that a NULL attribute is created.
+		entity->getArgument(i);
+	}
 	IfcSchema::Type::PopulateDerivedFields(writable_entity());
 }
 IfcParse::IfcLateBoundEntity::IfcLateBoundEntity(IfcAbstractEntity* e) {