fix: update selectedSelectedInternalAccount to not capture exceptions where the selectedAccount is emtpy (#34301)

## **Description**

This PR adds a check to make sure that there is a `selectedAccount`
before capturing an exception, otherwise we often get misreporting
during onboarding. This exception is most useful when we encounter
scenarios where a `selectedAccount` exists but the corresponding account
isn't in state.

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes: #29062

## **Manual testing steps**

N/A

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [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
- [x] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

#### Performance checks (if applicable)

- [x] I've tested on Android
  - Ideally on a mid-range device; emulator is acceptable
- [ ] 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
- [ ] 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
Guide](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/400085549067/Performance+Guide+for+Engineers).

## **Pre-merge reviewer checklist**

- [x] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [x] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Narrow selector and error-reporting change with no auth or data
handling impact; existing behavior for invalid non-empty IDs is
unchanged.
> 
> **Overview**
> **`selectSelectedInternalAccount`** no longer reports to Sentry when
the selected account id is an empty string and no matching account
exists. That case is treated as “no account selected” (common during
onboarding) instead of a missing-account error.
> 
> Sentry **`captureException`** still runs when a **non-empty** selected
id has no entry in the accounts map. Behavior for callers stays
**`undefined`** when nothing is selected; a test covers the empty-id
path.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
b1f95b5. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: hmalik88

app/selectors/accountsController.test.ts

@@ -137,6 +137,24 @@ describe('Accounts Controller Selectors', () => {
         errorMessage,
       );
     });
+
+    it('does not throw an error if the selected account ID is empty', () => {
+      const result = selectSelectedInternalAccount({
+        engine: {
+          backgroundState: {
+            AccountsController: {
+              ...MOCK_ACCOUNTS_CONTROLLER_STATE,
+              internalAccounts: {
+                ...MOCK_ACCOUNTS_CONTROLLER_STATE.internalAccounts,
+                selectedAccount: '',
+              },
+            },
+          },
+        },
+      } as RootState);
+      expect(result).toBeUndefined();
+      expect(mockedCaptureException).not.toHaveBeenCalled();
+    });
   });
   describe('selectInternalAccounts', () => {
     it(`returns internal accounts of the accounts controller sorted by the keyring controller's accounts`, () => {

app/selectors/accountsController.ts

@@ -118,13 +118,14 @@ export const selectSelectedInternalAccount = createSelector(
     const account = accounts[selectedAccountId];
 
     if (!account) {
-      const err = new Error(
-        `selectSelectedInternalAccount: Account with ID ${selectedAccountId} not found.`,
-      );
-      captureException(err);
-      return undefined;
+      if (selectedAccountId !== '') {
+        const err = new Error(
+          `selectSelectedInternalAccount: Account with ID ${selectedAccountId} not found.`,
+        );
+        captureException(err);
+      }
     }
-    return account;
+    return account ?? undefined;
   },
 );