False-positive when dereferencing an inline-initialized field from constructor body

```
@NullMarked
class Foo {
    private @Nullable Object mArgs = new Object();

    Foo() {
        mArgs.getClass();
    }
}
```

Gives:
```
Foo.java:9: warning: [NullAway] dereferenced expression mArgs is @Nullable
        mArgs.getClass();
             ^
    (see http://t.uber.com/nullaway )
```