Fix for index key error within renderer.

There are times we don't have a `last_model`, we check for failure.

guidance/models/_engine/_engine.py

@@ -214,12 +214,11 @@ def _msg_recv(engine_weakref: weakref.ReferenceType, message: GuidanceMessage) -
     elif isinstance(message, ExecutionCompletedMessage) and message.is_err:
         pass
     elif isinstance(message, (ExecutionCompletedMessage, OutputRequestMessage, TokensMessage)):
-        last_model: "Model" = engine.model_dict[message.last_trace_id]
-        last_trace_id = message.last_trace_id
-
         failed = False
         processed_gen_tokens: list[GenTokenExtra] = []  # suppress IDE warnings by definition
         try:
+            last_trace_id = message.last_trace_id
+            last_model: "Model" = engine.model_dict[message.last_trace_id]
             processed_gen_tokens = last_model.get_per_token_stats()
         except Exception as e:
             logger.error(f"Failed to get per token stats: {e}")

guidance/visual/_renderer.py

@@ -391,7 +391,7 @@ def update(self, message: GuidanceMessage) -> None:
         # Send outgoing messages to client
         for out_message in out_messages:
             if isinstance(out_message, TraceMessage):
-                logger.debug(f"RENDERER:out:{out_message}")
+                # logger.debug(f"RENDERER:out:{out_message}")
                 self._last_trace_id = out_message.trace_id
 
             self._messages.append(out_message)