[bump_20.10 backport ]Fix panic in agent#3032

thaJeztah wants to merge 1 commit intomoby:bump_20.10moby/swarmkit:bump_20.10from

thaJeztah:20.10_backport_fix_agent_panicthaJeztah/swarmkit:20.10_backport_fix_agent_panicCopy head branch name to clipboard