Ensure existing SimpliSafe notifications trigger event on HASS startup (#34232)

* Ensure existing SimpliSafe notifications trigger event on HASS startup

* Don't redefine a standing function each loop iteration

* Wait until HASS state is "running"

* Linting

* Linting

* Code review

* Code review

* Simplify

* Code review

* Cleanup

homeassistant/components/simplisafe/__init__.py

@@ -24,7 +24,7 @@ from homeassistant.const import (
     CONF_TOKEN,
     CONF_USERNAME,
 )
-from homeassistant.core import callback
+from homeassistant.core import CoreState, callback
 from homeassistant.exceptions import ConfigEntryNotReady
 from homeassistant.helpers import (
     aiohttp_client,
@@ -422,6 +422,12 @@ class SimpliSafe:
     @callback
     def _async_process_new_notifications(self, system):
         """Act on any new system notifications."""
+        if self._hass.state != CoreState.running:
+            # If HASS isn't fully running yet, it may cause the SIMPLISAFE_NOTIFICATION
+            # event to fire before dependent components (like automation) are fully
+            # ready. If that's the case, skip:
+            return
+
         old_notifications = self._system_notifications.get(system.system_id, [])
         latest_notifications = system.notifications