SingleFileFacebookMessengerChatLoader fails when the chat contains non-text contents such as stickers and photos.
Labels: name: area: doc loader, name: auto:bug

### System Info

langchain 0.0.353
Python 3.10.13 | packaged by Anaconda, Inc. | (main, Sep 11 2023, 13:24:38) [MSC v.1916 64 bit (AMD64)]
Windows 11

### Who can help?

_No response_

### Information

- [X] The official example notebooks/scripts
- [ ] My own modified scripts

### Related Components

- [ ] LLMs/Chat Models
- [ ] Embedding Models
- [ ] Prompts / Prompt Templates / Prompt Selectors
- [ ] Output Parsers
- [X] Document Loaders
- [ ] Vector Stores / Retrievers
- [ ] Memory
- [ ] Agents / Agent Executors
- [ ] Tools / Toolkits
- [ ] Chains
- [ ] Callbacks/Tracing
- [ ] Async

### Reproduction

```python
from langchain.chat_models.openai import ChatOpenAI
from langchain_community.chat_loaders.facebook_messenger import FolderFacebookMessengerChatLoader, SingleFileFacebookMessengerChatLoader
from pathlib import Path
import os

chat_file = Path("data/my-fb-folder/messages/inbox/message-dir/message_1.json")
loader = SingleFileFacebookMessengerChatLoader(chat_file)
loader.load()
```

Stacktrace:
```
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
Cell In[11], [line 8](vscode-notebook-cell:?execution_count=11&line=8)
      [6](vscode-notebook-cell:?execution_count=11&line=6) chat_file = Path("data/my-fb-folder/your_activity_across_facebook/messages/inbox/message-dir/message_1.json")
      [7](vscode-notebook-cell:?execution_count=11&line=7) loader = SingleFileFacebookMessengerChatLoader(chat_file)
----> [8](vscode-notebook-cell:?execution_count=11&line=8) loader.load()

File [c:\Users\th4tkh13m\miniconda3\envs\rag\lib\site-packages\langchain_community\chat_loaders\base.py:16](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/base.py:16), in BaseChatLoader.load(self)
     [14](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/base.py:14) def load(self) -> List[ChatSession]:
     [15](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/base.py:15)     """Eagerly load the chat sessions into memory."""
---> [16](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/base.py:16)     return list(self.lazy_load())

File [c:\Users\th4tkh13m\miniconda3\envs\rag\lib\site-packages\langchain_community\chat_loaders\facebook_messenger.py:43](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:43), in SingleFileFacebookMessengerChatLoader.lazy_load(self)
     [39](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:39) messages = []
     [40](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:40) for m in sorted_data:
     [41](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:41)     messages.append(
     [42](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:42)         HumanMessage(
---> [43](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:43)             content=m["content"], additional_kwargs={"sender": m["sender_name"]}
     [44](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:44)         )
     [45](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:45)     )
     [46](file:///C:/Users/th4tkh13m/miniconda3/envs/rag/lib/site-packages/langchain_community/chat_loaders/facebook_messenger.py:46) yield ChatSession(messages=messages)

KeyError: 'content'
```

### Expected behavior

The chat message should be loaded normally.