The duplicate condition of checking nullable file parameter while implementing multipart request

[tungpham6195]

Describe the bug
The issue is happening when I change the parameter to nullable. It only happens when the nullable parameter is without required keyword.

To Reproduce
Steps to reproduce the behavior:

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

Expected behavior
The generated code should contains the duplicate condition of checking nullable parameter.

Screenshots
The declaration of my method:

The generated codes:

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
The project is using retrofit_generator: 9.1.7