fix: SafeLocalStorage handle undefined value

[combab0]

Description

If localStorage.setItem('item', undefined) is executed, the string 'undefined' is stored as the value for 'item', which is a bug. SafeLocalStorage should avoid setting values in localStorage when the value is undefined to ensure safer behavior.

This patch also resolves the following currently occurring error:

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'toLowerCase')
    at AppKit.syncAccount (client.js:1069:1)
    at AppKit.syncExistingConnection (client.js:1213:1)
    at async AppKit.initialize (client.js:201:1)
syncAccount @ client.js:1069
syncExistingConnection @ client.js:1213
await in syncExistingConnection
initialize @ client.js:201
await in initialize
AppKit @ client.js:184
createAppKit @ react.js:16

Type of change

• Chore (non-breaking change that addresses non-functional tasks, maintenance, or code quality improvements)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Associated Issues

None

Showcase (Optional)

None

Checklist

• Code in this PR is covered by automated tests (Unit tests, E2E tests)
• My changes generate no new warnings
• I have reviewed my own code
• I have filled out all required sections
• I have tested my changes on the preview link
• Approver of this PR confirms that the changes are tested on the preview link

[changeset-bot]

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Latest commit: bf84d05

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[vercel]

@combab0 is attempting to deploy a commit to the Reown Team on Vercel.

A member of the Team first needs to authorize it.

[arein]

@combab0 can you add a test pls?

[magiziz]

Suggested change

	if (isSafe() && value !== undefined) {
	if (value && isSafe()) {

[tomiir]

Should not happen as they are strings but this might result in a weird behavior if value is false

[tomiir]

@arein adding a test in a PR now 🙏

Edit: #3502