* Add default expressions for ExpEvalReqHAdvice
https://stackoverflow.com/questions/54546728/how-to-handle-ftpoutboundadapter-connection-exception-in-spring-integration-flow
When channels are configured for the `ExpressionEvaluatingRequestHandlerAdvice`,
but no expressions, the logic is not performed.
In other words: we can evaluate expressions, when no channels,
but we don't send messages to channels when no expressions.
* Provide default expressions to be evaluated to `payload`, when only
channels are provided.
* * Remove asserts for expression setters
71fd60fda6