Fix mesh refinement for custom constraints

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (6197a3c) 94.10% compared to head (877e0d2) 94.10%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #79 +/- ## ======================================= Coverage 94.10% 94.10% ======================================= Files 75 75 Lines 5565 5565 ======================================= Hits 5237 5237 Misses 328 328 ``` | [Files Changed](https://app.codecov.io/gh/DanielVandH/DelaunayTriangulation.jl/pull/79?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniel+VandenHeuvel) | Coverage Δ | | |---|---|---| | [...c/data\_structures/refinement/refinement\_targets.jl](https://app.codecov.io/gh/DanielVandH/DelaunayTriangulation.jl/pull/79?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniel+VandenHeuvel#diff-c3JjL2RhdGFfc3RydWN0dXJlcy9yZWZpbmVtZW50L3JlZmluZW1lbnRfdGFyZ2V0cy5qbA==) | `66.66% <ø> (ø)` | | | [src/refinement/quality\_assessment.jl](https://app.codecov.io/gh/DanielVandH/DelaunayTriangulation.jl/pull/79?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniel+VandenHeuvel#diff-c3JjL3JlZmluZW1lbnQvcXVhbGl0eV9hc3Nlc3NtZW50Lmps) | `100.00% <100.00%> (ø)` | |

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