fix no cfg xtrig broadcast delta shutdown#6936

dwsutherland wants to merge 2 commits intocylc:8.5.xcylc/cylc-flow:8.5.xfrom

dwsutherland:no-xtrig-cfg-bc-error-fixdwsutherland/cylc-flow:no-xtrig-cfg-bc-error-fixCopy head branch name to clipboard