fix: Check that isUnlocked exists before calling

[usame-algan]

What it solves

Resolves #1134

How this PR fixes it

• Checks that the method exists before calling it

How to test

This error most likely happens with older versions of the metamask extension. It was implemented in 2018

• Connect to the safe via MM
• Lock the Account from MM
• Observe the wallet disconnecting in the safe

[github-actions]

ESLint Summary View Full Report

Annotations are provided inline on the Files Changed tab. You can also see all annotations that were generated on the annotations page.

Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: ✅ success
• Annotations: 0 total

---

^{Report generated by eslint-plus-action}

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Pages

Latest commit:	511b574
Status:	✅  Deploy successful!
Preview URL:	https://c418abec.web-core.pages.dev
Branch Preview URL:	https://isunlocked-error.web-core.pages.dev

View logs

[francovenica]

Note: is said that this was more of an issue with old versions of MM, but I don't think MM let you use such an old version of its extension so it should be fine

LGTM.
Locking the MM wallet disconnects you from the app.