[Bug] Unreachable code reached in AdminSpace

[JEnoch]

Describe the bug

Reported by "haklu" on Discord, and reproduced by @JEnoch.

Under the condition below, zenohd crashes on a GET on AdminSpace with this error:

thread 'async-std/runtime' panicked at 'internal error: entered unreachable code: An unresolved WireExpr (1:/**) reached the plugins, this shouldn't have happened, please contact us via GitHub or Discord.', zenoh/src/net/runtime/adminspace.rs:444:25
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

To reproduce

1. Start zenohd with the default config
2. Run this request: curl -H "Accept:text/event-stream" http://localhost:8000/@/**
3. Cancel it by pressing ctrl-c
4. Run this request: curl http://localhost:8000/@/**

System info

• Zenoh version: 0.6.0-beta.1