Use more reliable username variable in error log output

Author: emlun

webauthn-server-demo/src/main/scala/demo/webauthn/WebAuthnServer.java

@@ -269,7 +269,7 @@ public Either<List<String>, SuccessfulAuthenticationResult> finishAuthentication
                         } catch (Exception e) {
                             logger.error(
                                 "Failed to update signature count for user \"{}\", credential \"{}\"",
-                                request.getUsername(),
+                                username,
                                 response.getCredential().id(),
                                 e
                             );