Fix some code issues

[RainerKuemmerle]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 91.42857% with 3 lines in your changes missing coverage. Please review.

Project coverage is 66.28%. Comparing base (8443f08) to head (642d736).
Report is 3 commits behind head on pymem.

Files with missing lines	Patch %	Lines
g2o/solvers/pcg/linear_solver_pcg.h	87.50%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            pymem     #862      +/-   ##
==========================================
+ Coverage   65.74%   66.28%   +0.53%     
==========================================
  Files         342      342              
  Lines       13392    13407      +15     
  Branches     1316     1317       +1     
==========================================
+ Hits         8805     8887      +82     
+ Misses       4195     4116      -79     
- Partials      392      404      +12     

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