The second Rust session always fails

[sonnyp]

Steps to reproduce

0. flatpak kill re.sonny.Workbench.Devel
1. rm -rf ~/.var/app/re.sonny.Workbench.Devel
2. Start Workbench from main
3. Open any Rust demo
4. Press "Run" - it compiles and execute all good
5. Open any other Rust demo
6. Press "Run" - it fails with the following

thread '<unnamed>' panicked at code.rs:4:89:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5

It appears that running only works after a fresh cargo build?