Outdated documentation for email-link setup

[theHilikus]

Email-link signin was not working in my app when the email link was clicked in the Outlook app. I traced it to this line in the official documentation, which doesn't seem to have a good reason to exist, AFAICT

https://github.com/firebase/FirebaseUI-Android/blame/master/auth/README.md#L297

For some reason, the gmail app does have extras in the intent but not the outlook app. In any case, that null check seems unnecessary: nothing in the sample code in the README derefences getIntent().getExtras() and moreover, everything works fine even when extras is null. Is this just outdated documentation?

[samtstern]

That line was added here:
#1503

To be honest I am not sure what it was meant to do ... seems like you're right and we should probably remove it

[omaksymov]

@samtstern
Initial code reference is pointing to wrong part of README today, so more robust reference is:

FirebaseUI-Android/auth/README.md

Lines 374 to 376 in 980d0cc

	if (getIntent().getExtras() == null) {
	return;
	}

That code seemed to be in parity with this documentation - see sources in snippets-android repo: Kotlin, Java. And in fact it is outdated as pointed out in https://stackoverflow.com/questions/58350107/firebase-ui-email-link-signin-intent-extra-is-null.
So checking intent extras should be replaced with just intent.getData().toString() in all parts of related documentation. After doing this linter will warn about link being non-nullable, so if (link != null) check can be removed as well.