server.open fails to add slash before relative path

[milahu]

Describe the bug

i am doing

npx vite --open index.html

actual result: the relative path is joined with the port number

http://http//localhost:5178index.html

expected result: index.html should have the same meaning as /index.html

http://localhost:5178/index.html

related #5068

Reproduction

-

Steps to reproduce

No response

System Info

npx vite --version 
vite/3.1.7 linux-x64 node-v19.0.0

Used Package Manager

npm

Logs

No response

Validations

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