urosbericsyrmia

This issue should be fixed by [llvm/llvm-project#80799](https://github.com/llvm/llvm-project/pull/80799). Initially, the cause of the issue and the solution are explained in [llvm/llvm-project#80666](https://github.com/llvm/llvm-project/pull/80666), but more elegant solution is just to remove derived isBlockOnlyReachableByFallthrough...