[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[X] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

When i call form reset on a formGroup with nested formGroup passing it with a null value i receive a error "Cannot read property ... of null"

Expected behavior

Expected result is that on form reset with a null value the nested form group properties become all null.

Minimal reproduction of the problem with instructions

When i have a formGroup with a nested formGroup like this:

let form = this.fb.group({
Id: [null],
Nested: fb.group({
    Id: [null]
})
})

If i call a form reset or a patch value with a object like this:

form.reset({
Id: 1,
Nested: null
})

i receive the error "Cannot read property 'Id' of null" because he try to read the nested property from a null object

Expected result is that on form reset with a null value the nested form group properties become all null. This behavior happen when i call the reset without the nested properties:
form.reset({Id: 3})

What is the motivation / use case for changing the behavior?

Usually service return models with all properties and nested entities null if they don't exist instead return the nested entities initialized