controller: Fix validation error return when getting active formations
controller: Fix validation error return when getting active formations

Signed-off-by: Lewis Marshall <748e1641a368164906d4a0c0e3965345453dcc93@lmars.net>

benbjohnson/flynn,lmars/flynn,philiplb/flynn,philiplb/flynn,benbjohnson/flynn,lmars/flynn,benbjohnson/flynn,philiplb/flynn,benbjohnson/flynn,flynn/flynn,flynn/flynn,lmars/flynn,flynn/flynn,lmars/flynn,benbjohnson/flynn,benbjohnson/flynn,flynn/flynn,lmars/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn