Crash in compiler

[hunger]

Bug Description

The following piece of code crashes the compiler for me:

Reproducible Code (if applicable)

export component MainWindow inherits Window{
    in-out property <int> some_prop: 42;
}
export { MainWindow as Main-Window }

Environment Details

• Slint Version: master
• Platform/OS: Linux
• Programming Language: None
• Backend/Renderer: None

Product Impact

No response

[hunger]

The use case is the minimized result from the fuzzer. I can reproduce this in slintpad.com

[ogoffart]

panicked at internal/compiler/passes/generate_item_indices.rs:93:67:
called `Result::unwrap()` on an `Err` value: 0

This is the same as #6559 and #7029