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Partly, this is my fault -- val is not that useful in the @Model context, since @Model relies on mutability. I am used to thinking in terms of immutable viewstates and screwed this up.

However, it probably should not crash this way. Either it should work (with a never-changing value) or it should fail with a "are you *really* sure you want this here?" sort of error.

I'd like to add that declaring `canProceed` as a `var` won't crash the app.
The extension function is avoidable by just having the `get()`-getter function inside the class itself. That also avoids the crash.