If a promise is resolved with a null or undefined value, the fullfilled action will not include a payload property. This is because actions describe changes in state. Consider the following two actions:
// A
{
type: 'ACTION`,
meta: ...
}
// B
{
type: 'ACTION'
payload: null,
meta: ...
}
Both actions describe the same change in state. This is why, when you resolve with null or undefined, the payload property is not included. It would be redundant to include it.