No FAA0001 when `?.` is followed by `Should().BeApproximately`

Suppose for the sake of this bug report that we have the following type:

public interface IExample {
    double Amount { get; }
}

Then if we write the following incorrect test:

public void TestMethod() {
    IExample? actual = null;

    actual?.Amount.Should().BeApproximately(3.14, 0.01);   // no FAA0001 here?!
}

then we get no message from FluentAssertions.Analyzers about the wrong code.

For other assertions, this works fine. For example:

    actual?.Amount.Should().BeGreaterThan(3.1);  // good, we get 'FAA0001: Use .Should() instead of ?.Should()'

or:

    actual?.Amount.Should().BePositive();  // good, we get 'FAA0001: Use .Should() instead of ?.Should()'

or:

    actual?.Amount.Should().BeInRange(3.1, 3.2);  // good, we get 'FAA0001: Use .Should() instead of ?.Should()'

We need the FAA0001 with .BeApproximately(3.14, 0.01) as well. Without it, the author may think his tests proves actual is an instance where Amount equals 3.14 within a tolerance of 0.01 when in fact actual is a null reference (and no Amount exists).

Inizia riproducendo il problema con l'esempio C# usando actual?.Amount.Should().BeApproximately(3.14, 0.01), quindi confronta la gestione di FAA0001 per BeApproximately con BeGreaterThan, BePositive e BeInRange. Il lavoro è completato quando l'analizzatore segnala FAA0001 per il caso BeApproximately, mantenendo il comportamento esistente per le altre assertions.