Fix size check in Model::setStateIsNonNegative

[dweindl]

Previously, the wrong array was checked 🙈:

amici_model.setAllStatesNonNegative() # works as expected
amici_model.setStateIsNonNegative([]) # should fail
amici_model.setAllStatesNonNegative() # should work, but fails

Traceback (most recent call last):
  File "<ipython-input-22-d7056e8e4e3f>", line 1, in <module>
    amici_model.setAllStatesNonNegative()
  File "python/sdist/amici/amici.py", line 2243, in setAllStatesNonNegative
    return _amici.ModelPtr_setAllStatesNonNegative(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: Dimension of input stateIsNonNegative (0) does not agree with number of state variables (2)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.88%. Comparing base (4782cad) to head (28352d9).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2332   +/-   ##
========================================
  Coverage    77.88%   77.88%           
========================================
  Files          324      324           
  Lines        20680    20680           
  Branches      1440     1440           
========================================
  Hits         16107    16107           
  Misses        4570     4570           
  Partials         3        3           

Flag	Coverage Δ
cpp	73.67% <100.00%> (ø)
cpp_python	34.36% <0.00%> (ø)
petab	36.90% <0.00%> (ø)
python	72.48% <0.00%> (ø)
sbmlsuite	?

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Files	Coverage Δ
src/model.cpp	86.24% <100.00%> (ø)