fix(web): use null for null body responses

[pi0]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Reported by @Atinux > @danielroe

This fixes the issue with null body responses in h3. Once nitro migrates to the web handler, it should fix all possible targets.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #495 (b7b15f7) into main (f3394ee) will increase coverage by 0.01%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##             main     #495      +/-   ##
==========================================
+ Coverage   82.37%   82.38%   +0.01%     
==========================================
  Files          31       31              
  Lines        3500     3508       +8     
  Branches      522      523       +1     
==========================================
+ Hits         2883     2890       +7     
- Misses        617      618       +1     

Files Changed	Coverage Δ
src/adapters/web.ts	98.03% <88.88%> (-1.97%)	⬇️