Just upgraded to HA 0.50.2 and received this error in the frontend…
In the log, it says…
ERROR (MainThread) [homeassistant.config] Invalid config for [automation]: [state] is an invalid option for [automation]. Check: automation->trigger->0->state. (See /home/pi/.homeassistant/configuration.yaml, line XXX). Please check the docs at https://home-assistant.io/components/automation/