Not inferring from a first filter in case of two consecutive filters

Found this false positive in the code while using.

  class Aclass {

      class Name {
          @Nullable String firstName;
          @Nullable String lastName;
          @Nullable String middleName;
      }

      @Contract("null -> true")
      public boolean isBlank(@Nullable String string) {
          return string == null || string.trim().length() == 0;
      }

      private Observable<Integer> filterThenMap(Observable<Name> observable) {
          return observable
                  .filter(name -> !isBlank(name.firstName) && name.middleName!=null)
                  .filter(name -> name.lastName!=null)
                  .map(name -> name.firstName.length());
      }
  }

This gives warning: [NullAway] dereferenced expression name.firstName is @Nullable at
.map(name -> name.firstName.length());

Start by reproducing the warning with the consecutive-filter example in the issue. Trace how NullAway carries nullness facts from one filter predicate into the next, and consider the issue done when the final map expression is accepted without a false-positive warning.