Builds the carrier for the settings, or undefined when none are given or the type is unknown (logged: a typo in the carrier type must be visible, but a missing carrier block is allowed because the check is optional).
undefined
Builds the carrier for the settings, or
undefinedwhen none are given or the type is unknown (logged: a typo in the carrier type must be visible, but a missing carrier block is allowed because the check is optional).