### What
minor fix to match behavior to ae10b5c82b/packages/next/src/shared/lib/router/utils/remove-trailing-slash.ts (L2C4-L9)
as we're seeing a panic when route is /
```
Panic: PanicInfo { payload: Any { .. }, message: Some(byte index 1 is out of bounds of ``), location: Location { file: "packages/next-swc/crates/next-core/src/next_edge/route_regex.rs", line: 202, col: 59 }, can_unwind: true, force_no_backtrace: false }
Backtrace: 0: backtrace::backtrace::libunwind::trace
```
Closes WEB-1841