fix(sessions): guard None event.actions before reading state_delta

BaseSessionService guards `event.actions` for None before reading
state_delta in _apply_temp_state, _trim_temp_delta_state, and
_update_session_state, matching prior behavior for callers that
build events with actions unset. InMemorySessionService applies the
same guard in append_event.

Change-Id: I6598ac68711ebb360f8081c2f895e1dc17942ad5

Author: GWeale

src/google/adk/sessions/base_session_service.py

@@ -138,7 +138,7 @@ def _apply_temp_state(self, session: Session, event: Event) -> None:
     the duration of the current invocation but is NOT persisted to storage
     (the event delta is trimmed separately by _trim_temp_delta_state).
     """
-    if not event.actions.state_delta:
+    if not event.actions or not event.actions.state_delta:
       return
     for key, value in event.actions.state_delta.items():
       if key.startswith(State.TEMP_PREFIX):
@@ -151,7 +151,7 @@ def _trim_temp_delta_state(self, event: Event) -> Event:
     in-memory session state (updated by _apply_temp_state) retains the
     values for the duration of the current invocation.
     """
-    if not event.actions.state_delta:
+    if not event.actions or not event.actions.state_delta:
       return event
 
     event.actions.state_delta = {
@@ -163,7 +163,7 @@ def _trim_temp_delta_state(self, event: Event) -> Event:
 
   def _update_session_state(self, session: Session, event: Event) -> None:
     """Updates the session state based on the event."""
-    if not event.actions.state_delta:
+    if not event.actions or not event.actions.state_delta:
       return
     for key, value in event.actions.state_delta.items():
       session.state.update({key: value})

src/google/adk/sessions/in_memory_session_service.py

@@ -346,7 +346,7 @@ def _warning(message: str) -> None:
       storage_session.events.append(event)
       storage_session.last_update_time = event.timestamp
 
-    if event.actions.state_delta:
+    if event.actions and event.actions.state_delta:
       state_deltas = _session_util.extract_state_delta(
           event.actions.state_delta
       )