Outbound Route with no 'enabled trunks' will not fall through to next outbound route

While doing some testing with specific routes for some specific numbers, I disabled
a trunk, and found that any calls made which matched the outbound route were
flagged as ‘service unavailable’ because there was no available trunk.

It would make sense that if a trunk is disabled, then any outbound routes, which no
longer have any enabled trunks, should be left out of the dial plan, allowing subsequent
outbound routes to match if they exist.

Any suggestions?