fix: handle missing agent name in readonly context

Author: he-yufeng

src/google/adk/agents/readonly_context.py

@@ -49,6 +49,8 @@ def invocation_id(self) -> str:
   @property
   def agent_name(self) -> str:
     """The name of the agent that is currently running."""
+    if self._invocation_context.agent is None:
+      return "unknown"
     return self._invocation_context.agent.name
 
   @property

tests/unittests/agents/test_readonly_context.py

@@ -39,6 +39,12 @@ def test_agent_name(mock_invocation_context):
   assert readonly_context.agent_name == "test-agent-name"
 
 
+def test_agent_name_without_agent(mock_invocation_context):
+  mock_invocation_context.agent = None
+  readonly_context = ReadonlyContext(mock_invocation_context)
+  assert readonly_context.agent_name == "unknown"
+
+
 def test_state_content(mock_invocation_context):
   readonly_context = ReadonlyContext(mock_invocation_context)
   state = readonly_context.state