Fix regression from 648d5ae

[Jarred-Sumner]

What does this PR do?

Fix regression from 648d5ae

In certain cases, Bun.serve() was sending a 0\r\n\r\n chunk when using the Content-Length header after the data has already been fully sent, which was invalid. When HTTP clients receive this, they disconnect. This caused a performance regression, but doesn't appear to have caused issues otherwise.

How did you verify your code works?

There are tests

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on linux-x64:

• test/js/third_party/prisma/prisma.test.ts 1 failing

View test output

^{#d3070ba8cb792d0fa461df1e573354bb67e0520a}

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on linux-x64-baseline:

• test/js/third_party/prisma/prisma.test.ts 1 failing

View test output

^{#d3070ba8cb792d0fa461df1e573354bb67e0520a}

[github-actions]

❌ @Jarred-Sumner 2 files with test failures on bun-darwin-aarch64:

• test/integration/next/default-pages-dir/test/dev-server.test.ts 2 failing
• test/js/third_party/prisma/prisma.test.ts 1 failing

View test output

^{#d3070ba8cb792d0fa461df1e573354bb67e0520a}

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on bun-darwin-x64:

• test/js/third_party/prisma/prisma.test.ts 2 failing

View test output

^{#d3070ba8cb792d0fa461df1e573354bb67e0520a}

[github-actions]

❌🪟 @Jarred-Sumner, there are 12 test regressions on Windows x86_64

• test\cli\run\transpiler-cache.test.ts
• test\js\bun\dns\resolve-dns.test.ts
• test\js\bun\http\fetch-file-upload.test.ts
• test\js\bun\http\bun-server.test.ts
• test\js\bun\shell\shelloutput.test.ts
• test\js\bun\shell\throw.test.ts
• test\js\node\dns\node-dns.test.js
• test\js\node\process\process-args.test.js
• test\js\web\fetch\body-stream-excess.test.ts
• test\js\web\fetch\body-stream.test.ts
• test\js\web\websocket\websocket.test.js
• test\js\web\workers\worker.test.ts

Full Test Output