Fixes from benchmark

[mateuszbaran]

Since the benchmark in #339 is not ready yet, I've extracted the bugfixes to a separate branch.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (da84054) 99.79% compared to head (eabea17) 99.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #341      +/-   ##
==========================================
- Coverage   99.79%   99.60%   -0.19%     
==========================================
  Files          69       69              
  Lines        6361     6372      +11     
==========================================
- Hits         6348     6347       -1     
- Misses         13       25      +12     

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[kellertuer]

I am not sure where we lose the subsolver gradient access test but the Wolfe-conidtion one is one that is definelty unrelated to the changes here. If you have a moment, taking a look would be great but otherwise this is also fine.

[mateuszbaran]

I think we can leave that coverage issue for later.