fix: invoice ocr assistant

Currently, the invoice_ocr_assistant example cannot run, it will
complain about the index out of range exceptions. The problem comes from
adding actions in _act() but do not update the state and max_react_loop.

The solution is copied from tutorial_assistants.py.

metagpt/roles/invoice_ocr_assistant.py

@@ -80,19 +80,17 @@ class InvoiceOCRAssistant(Role):
                 raise Exception("Invoice file not uploaded")
 
             resp = await todo.run(file_path)
+            actions = list(self.actions)
             if len(resp) == 1:
                 # Single file support for questioning based on OCR recognition results
-                self.set_actions([GenerateTable, ReplyQuestion])
+                actions.extend([GenerateTable, ReplyQuestion])
                 self.orc_data = resp[0]
             else:
-                self.set_actions([GenerateTable])
-
-            self.set_todo(None)
+                actions.append(GenerateTable)
+            self.set_actions(actions)
+            self.rc.max_react_loop = len(self.actions)
             content = INVOICE_OCR_SUCCESS
             resp = OCRResults(ocr_result=json.dumps(resp))
-            msg = Message(content=content, instruct_content=resp)
-            self.rc.memory.add(msg)
-            return await super().react()
         elif isinstance(todo, GenerateTable):
             ocr_results: OCRResults = msg.instruct_content
             resp = await todo.run(json.loads(ocr_results.ocr_result), self.filename)