null safe issue

[nxnote]

Describe the bug
As the dependencies: archive: ^4.0.7
this cause issue of null safe.

Error message shows:
docx_creator-1.1.1/lib/src/exporters/docx_exporter.dart(227,15): error G7C168647: Property 'isEmpty' cannot be accessed on 'List?' because it is potentially null.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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[nxnote]

Please fix it in the next version:

    final bytes = encoder.encode(archive);

    if (bytes == null || bytes.isEmpty) {
      throw DocxExportException('Failed to encode ZIP', targetFormat: 'DOCX');
    }

    return Uint8List.fromList(bytes);

[alihassan143]

@nxnote kindly provide some sample code because in my tests i didn't get that error