authority_authenticate() was returning success if authority was NULL, this

is an error for all the other authority_* APIs, now it is here, as well.

@@ -221,7 +221,7 @@ authority_authenticate (authority_t authority)
     {
     {
       return authority->_authenticate (authority);
       return authority->_authenticate (authority);
     }
     }
-  return 0;
+  return EINVAL;
 }
 }
 
 
 int
 int