null cast away in valueChanges()

[timblakely]

AngularFire:

5.0.0-rc.3

If the document does not exist, this line returns action.payload.data() : null, which is in turn casted to T, dropping the null case. Seems like the return type for valueChanges() should be Observable<T|null>.

[davideast]

@timblakely Yep, it sure should! Care to make the PR?

[larssn]

But any type can always implicitly be null. Observable<T|null> is the same as Observable<T>.

VSCode will even ignore the |null part of a return type.

EDIT
Ignore what I said; with strictNullChecks enabled, it is still relevant.