runtime error

Exit code: 1. Reason: Traceback (most recent call last): File "/home/user/app/app.py", line 25, in <module> line_handler = WebhookHandler(os.getenv('LINE_CHANNEL_SECRET')) File "/usr/local/lib/python3.10/site-packages/linebot/v3/webhook.py", line 162, in __init__ self.parser = WebhookParser(channel_secret) File "/usr/local/lib/python3.10/site-packages/linebot/v3/webhook.py", line 120, in __init__ self.signature_validator = SignatureValidator(channel_secret) File "/usr/local/lib/python3.10/site-packages/linebot/v3/webhook.py", line 75, in __init__ self.channel_secret = channel_secret.encode('utf-8') AttributeError: 'NoneType' object has no attribute 'encode'

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