SAML warning, null Reference URI or its Transforms

I have a client that is configured with SAML.
After upgrading to Keycloak 15.0.2 I get the warn:
WARN - The input bytes to the digest operation are null. This may be due to a problem with the Reference URI or its Transforms. [1]

Should I care about that?

I should add that when checking the SAMLResponse The Reference URI and its Transforms are all filled with a value.