eventmanager: avoid using the wrong index on grouphash
eventmanager: avoid using the wrong index on grouphash

This is a slight behavior change, but shouldn't be wrong. This is being
done to mitigate an immediate issue and should be assessed later.

/cc @tkaemming

beeftornado/sentry,gencer/sentry,jean/sentry,ifduyue/sentry,ifduyue/sentry,looker/sentry,JackDanger/sentry,ifduyue/sentry,JackDanger/sentry,beeftornado/sentry,jean/sentry,mvaled/sentry,looker/sentry,ifduyue/sentry,gencer/sentry,mvaled/sentry,looker/sentry,mvaled/sentry,mvaled/sentry,looker/sentry,jean/sentry,ifduyue/sentry,jean/sentry,gencer/sentry,beeftornado/sentry,gencer/sentry,gencer/sentry,looker/sentry,jean/sentry,mvaled/sentry,JackDanger/sentry,mvaled/sentry