Guard against undefined verificationUri and userCode in device code flow

[eschoeller]

Summary

• Add null check on response.verificationUri before calling browserUtil.open() in processDeviceCodeCallback
• Add null check on response.userCode before calling clipboardy.writeSync()

Both crash with TypeError when the MSAL DeviceCodeResponse does not populate these fields and autoOpenLinksInBrowser or copyDeviceCodeToClipboard are enabled.

Closes #7167

[Adam-it]

@eschoeller thanks for openning the PR but lets keep it draft for now since I cannot seem to be able to reporduce the bug you described

[eschoeller]

Oh sure, that's a good idea. Should have I sent it as a draft initially? I haven't been able to actually use the CLI much yet - waiting on my org to enable a few more things .. but I did encounter this issue. I'd be happy to test it again, perhaps it's been fixed somehow now. It was well over a week ago when I stumbled into it the first time at this point.

I have a few more fixes/features queued up too.

Thanks!