[BUG] CLI crashes with TypeError when AsyncAPI document file is empty

### Describe the bug.

When running the AsyncAPI CLI with an empty AsyncAPI file, the CLI crashes with a raw JavaScript TypeError instead of showing a user-friendly validation error.

### Expected behavior

The CLI should detect that the AsyncAPI file is empty and return a clear error message, such as:

`The provided AsyncAPI file is empty or invalid.`

### Screenshots

### How to Reproduce

1. Create an empty AsyncAPI file:
```
touch empty.yaml
```

2. Create a minimal valid generator template:
```
mkdir -p test-template/template
cat > test-template/package.json <=2.0.0"
}
EOF
echo "test" > test-template/template/test.txt
```

3. Run the AsyncAPI CLI:
```
asyncapi generate fromTemplate empty.yaml ./test-template -o out
```

### 🖥️ Device Information [optional]

- Operating System (OS): Windows(WSL)
- Browser:
- Browser Version:

### 👀 Have you checked for similar open issues?

- [x] I checked and didn't find similar issue

### 🏢 Have you read the Contributing Guidelines?

- [x] I have read the [Contributing Guidelines](https://github.com/asyncapi/.github/blob/master/CONTRIBUTING.md)

### Are you willing to work on this issue ?

yes