C#: Eliminate bad magic optimization
C#: Eliminate bad magic optimization

```
[2022-01-14 08:57:14] (253s) Tuple counts for Stmt::getAChild#bbf/3@8dfbc66f after 1m53s:
                      4922010396 ~5%     {3} r1 = JOIN ControlFlowElement::ControlFlowElement::getEnclosingCallable_dispred#ff_10#join_rhs WITH ControlFlowElement::ControlFlowElement::getEnclosingCallable_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1 'cfe', Rhs.1 'cfe', Lhs.0 'c'
                      1597068    ~2%     {3} r2 = JOIN r1 WITH Element::Element::getAChild_dispred#ff ON FIRST 2 OUTPUT Lhs.0 'cfe', Lhs.2 'c', Lhs.1 'result'
                                         return r2
```

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