I am getting following error "readStartArray can only be called when CurrentBSONType is ARRAY, not when CurrentBSONType is NULL"

It is trying to convert into List<List<T>>
and data in mongo is
[
[

{ "id" : 10927809, }

,

{ "id" : 10927810, }

],
null
]
I am using mongo 3.6 with java async driver 3.6