VertexAI `SafetyRating.blocked` is `undefined`.

[dlarocque]

Operating System

n/a

Environment (if applicable)

n/a

Firebase SDK Version

11.4.0

Firebase SDK Product(s)

VertexAI

Project Tooling

TypeScript

Detailed Problem Description

SafetyRating.blocked is a required property, but it is undefined when it is not true. The default value should be false, or the type should be optional

See https://github.com/firebase/firebase-ios-sdk/blob/1d32f365dea853d543e0f111a67d458e6cc49f35/FirebaseVertexAI/Sources/Safety.swift#L290

Steps and code to reproduce issue

call generateContent() with a prompt that will be blocked due to safety settings.

[gioboa]

Can I take this one?