Debug This Error

I'll paste an error message or stack trace. Help me debug it:

1. **Identify the error type** — What kind of error is this? (syntax, runtime, type, network, etc.)
2. **Root cause** — Explain what's actually going wrong and why.
3. **Fix** — Provide the corrected code with an explanation of the change.
4. **Prevention** — Suggest how to avoid this error in the future (linting rules, type guards, error boundaries, etc.)

If the error is ambiguous without more context, ask me for the relevant code surrounding the error. Always explain the fix in plain English before showing code.