Don't update state interfaces if command interfaces are not finite

[christophfroehlich]

As reported by @MarqRazz: In setups with calculate_dynamics=false and where the command_interfaces don't have initial values, the state interfaces were overwritten with NaNs.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.57%. Comparing base (38110f4) to head (7d5c4ae).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...e_interface/src/mock_components/generic_system.cpp	33.33%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2786      +/-   ##
==========================================
- Coverage   89.60%   89.57%   -0.03%     
==========================================
  Files         152      152              
  Lines       17719    17720       +1     
  Branches     1456     1457       +1     
==========================================
- Hits        15877    15873       -4     
- Misses       1254     1258       +4     
- Partials      588      589       +1     

Flag	Coverage Δ
unittests	89.57% <33.33%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rface/test/mock_components/test_generic_system.cpp	99.76% <ø> (ø)
...e_interface/src/mock_components/generic_system.cpp	85.49% <33.33%> (-0.33%)	⬇️

... and 2 files with indirect coverage changes

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