Append one more possibility to the error message given for InvalidNonceReferrer

[atom-box]

The error message is in the JSON table here plugins/Login/lang/en.json

Expected
"InvalidNonceReferrer": "The form security failed because of an invalid "Referer" header. If you are using a proxy server, you must %1$sconfigure Matomo to accept the proxy header%2$s that forwards the host header. Also, check that your "Referer" header is sent correctly. If you previously connected using HTTPS, please ensure you are connecting over a secure (SSL/TLS) connection and try again. Also check that allowedReferrerHost is not NULL"

Actual
"InvalidNonceReferrer": "The form security failed because of an invalid "Referer" header. If you are using a proxy server, you must %1$sconfigure Matomo to accept the proxy header%2$s that forwards the host header. Also, check that your "Referer" header is sent correctly. If you previously connected using HTTPS, please ensure you are connecting over a secure (SSL/TLS) connection and try again."

[atom-box]

This is in response to the following user email:

(The error message for InvalidNonceReferrer) tells me the Referrer is not set correctly, but var_dump shows it set just perfectly. The real problem is that allowedReferrerHost is NULL and it's very unclear where allowedReferrerHost is supposed to be configured.

I traced this back to Nonce.php where it appears to be triggered by $allowedReferrerhost being NULL. $referrer is set correctly to "https://s.wanwire.com".

(I managed to get around it, but the error message is both incorrect and unhelpful.)

[sgiehl]

I don't think this addition will bring any benefit to the (end) users, as they wouldn't be able to change anything. The allowedReferrerHost is provided in the code and null is actually valid.
If there is a specific problem where that check fails we should look at that place.