It looks like you are trying to read an attribute from an empty entity.
To fix this you should check if the object exist ($Entity != empty). Maybe use a Datasource Microflow to debug.
This error message usually indicates that you are trying to access a property of a null object. In the context of a grant chart, it could mean that you are trying to access the value of a property that has not been properly initialized.
Gantt need row entity and microflow that return list and must have
and i have microflow ( required in gantt ) that return in list
but i show error like this
How cloud i resolve this problem