Fix bug when setting a quadratic objective

[odow]

Closes #148

We obviously need to add tests to MOI for this.

[chriscoey]

Thanks Oscar!

[codecov[bot]]

Codecov Report

Base: 81.66% // Head: 81.80% // Increases project coverage by +0.14% :tada:

Coverage data is based on head (825c8ad) compared to base (de4a6c1). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #149 +/- ## ========================================== + Coverage 81.66% 81.80% +0.14% ========================================== Files 3 3 Lines 1505 1506 +1 ========================================== + Hits 1229 1232 +3 + Misses 276 274 -2 ``` | [Impacted Files](https://codecov.io/gh/jump-dev/HiGHS.jl/pull/149?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jump-dev) | Coverage Δ | | |---|---|---| | [src/MOI\_wrapper.jl](https://codecov.io/gh/jump-dev/HiGHS.jl/pull/149?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jump-dev#diff-c3JjL01PSV93cmFwcGVyLmps) | `91.58% <100.00%> (+0.16%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jump-dev). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jump-dev)

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