The 409 release includes "system flows" to propagate %flubbing information over over the network. This allows us to mitigate a very common problem scenario where a ship is trying to poke another ship on an app they've never installed.

The system flow machinery causes annoying but harmless crashes on ships that are not yet up to date. This PR removes the printing of the stacktrace that will get progressively more annoying now that 409 is getting tested on real ships.