Check Config Value for idp_certs

Applied patch to resolve the issue.

Updated patch for samlauth 8.x-3.10.

In the case that $certs is not set, there should be a conditional check beforehand, to avoid PHP warning messages.

I don't think so: $certs can never be "not set"; if the config value is not set, $certs becomes an empty array. See the line just above what you patched:

$certs = $config->get('idp_certs') ?? [];

It could be that in your case, the 'idp_certs' value is set to an empty string or other empty scalar value.

But that really is a misconfiguration on your side. 'idp_certs' has never been a scalar value. And especially now that we have config validation, we can expect this to be a valid value. Besides, it's only a PHP warning, not a fatal error.

So the solution is just to fix your configuration values.