* @ctx: a tal context, or NULL.
* @errorstr: a string to prepend calls to error_fn, or NULL.
*
* This sanity-checks a tal tree (unless NDEBUG is defined, in which case
* it simply returns true). If errorstr is not null, error_fn is called
* when a problem is found, otherwise it is not.
* @ctx: a tal context, or NULL.
* @errorstr: a string to prepend calls to error_fn, or NULL.
*
* This sanity-checks a tal tree (unless NDEBUG is defined, in which case
* it simply returns true). If errorstr is not null, error_fn is called
* when a problem is found, otherwise it is not.