Ensures that the <code>aggregate</code> method argument is not <code>null</code> and
<code>aggregate.{@link hunt.shiro.authc.AuthenticationInfo#getPrincipals() getPrincipals()}</code>
is not <code>null</code>, and if either is <code>null</code>,
that none of the realms authenticated successfully.
Ensures that the <code>aggregate</code> method argument is not <code>null</code> and <code>aggregate.{@link hunt.shiro.authc.AuthenticationInfo#getPrincipals() getPrincipals()}</code> is not <code>null</code>, and if either is <code>null</code>, that none of the realms authenticated successfully.