Don't unwrap Conversion

[codecov[bot]]

Codecov Report

Patch coverage: 83.33% and project coverage change: +0.04% :tada:

Comparison is base (414e1c5) 27.56% compared to head (28618f0) 27.61%.

:exclamation: Current head 28618f0 differs from pull request most recent head df69efb. Consider uploading reports for the commit df69efb to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #545 +/- ## ========================================== + Coverage 27.56% 27.61% +0.04% ========================================== Files 80 80 Lines 8380 8384 +4 ========================================== + Hits 2310 2315 +5 + Misses 6070 6069 -1 ``` | [Files Changed](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/545?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/Operators/banded/Conversion.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/545?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9iYW5kZWQvQ29udmVyc2lvbi5qbA==) | `26.56% <50.00%> (-0.43%)` | :arrow_down: | | [src/Operators/Operator.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/545?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9PcGVyYXRvci5qbA==) | `51.98% <100.00%> (+0.10%)` | :arrow_up: | | [src/Operators/general/algebra.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/545?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9nZW5lcmFsL2FsZ2VicmEuamw=) | `66.22% <100.00%> (+0.79%)` | :arrow_up: |

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