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https://consensyssoftware.atlassian.net/browse/RWDS-1267
The Rewards crash likely came from an older persisted Rewards Redux
state that did not have newer array fields, especially campaigns. On
affected devices, selectCampaigns could return undefined.

It was account/device dependent because persisted state differs per
user/install.

Fix Applied: hardened both the restore path and selector path to
fallback to initial state (empty array or object instead of undefined)

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CHANGELOG entry: null

Fixes: https://consensyssoftware.atlassian.net/browse/RWDS-1267

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

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- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
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- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
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guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

- [x] I've tested on Android
  - Ideally on a mid-range device; emulator is acceptable
- [x] I've tested with a power user scenario
- Use these [power-user
SRPs](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/edit-v2/401401446401?draftShareId=9d77e1e1-4bdc-4be1-9ebb-ccd916988d93)
to import wallets with many accounts and tokens
- [x] I've instrumented key operations with Sentry traces for production
performance metrics
- See [`trace()`](/app/util/trace.ts) for usage and
[`addToken`](/app/components/Views/AddAsset/components/AddCustomToken/AddCustomToken.tsx#L274)
for an example

For performance guidelines and tooling, see the [Performance
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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: changes are defensive fallbacks for missing/undefined
persisted state and selector inputs, with added tests; behavior should
only differ for legacy/partial states.
>
> **Overview**
> Prevents Rewards tab crashes caused by older/partial persisted
Redux/controller state by **defaulting missing fields to safe empty
values**.
>
> Selectors and rehydrate logic now coalesce `undefined` arrays/objects
(e.g., `campaigns`, season arrays, `benefits`, dismissed-toasts map,
controller `accounts`/`subscriptions`) to empty defaults, and
`RewardsController` default state was extracted into `defaultState.ts`
and reused. Test coverage was expanded to lock in these
upgrade/undefined-state behaviors.
>
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
d7b351d. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->