A variation of {@link #getAccessor(hunt.stomp.Message, Class)}
with a {@code MessageHeaders} instance instead of a {@code Message}.
<p>This is for cases when a full message may not have been created yet.
@param messageHeaders the message headers to get an accessor for
@param requiredType the required accessor type (or {@code null} for any)
@return an accessor instance of the specified type, or {@code null} if none
@since 4.1
A variation of {@link #getAccessor(hunt.stomp.Message, Class)} with a {@code MessageHeaders} instance instead of a {@code Message}. <p>This is for cases when a full message may not have been created yet. @param messageHeaders the message headers to get an accessor for @param requiredType the required accessor type (or {@code null} for any) @return an accessor instance of the specified type, or {@code null} if none @since 4.1