Fix/aplot index error

[germa89]

I have seen this error randomly in few places in the CICD:

WARNING: /home/runner/work/pymapdl/pymapdl/examples/00-mapdl-examples/lathe_cutter.py failed to execute correctly: Traceback (most recent call last):
  File "/home/runner/work/pymapdl/pymapdl/examples/00-mapdl-examples/lathe_cutter.py", line 164, in <module>
    mapdl.vplot(
  File "/opt/hostedtoolcache/Python/3.9.15/x64/lib/python3.9/site-packages/ansys/mapdl/core/mapdl.py", line 1433, in vplot
    out = self.aplot(
  File "/opt/hostedtoolcache/Python/3.9.15/x64/lib/python3.9/site-packages/ansys/mapdl/core/mapdl.py", line 15[72](https://github.com/pyansys/pymapdl/actions/runs/3689261536/jobs/6245029261#step:16:73), in aplot
    area_color = rand[anum]
IndexError: index 1 is out of bounds for axis 0 with size 1

Link: https://github.com/pyansys/pymapdl/actions/runs/3689261536/jobs/6245029261#step:16:77

This comes from:

  if color_areas:
      anum = surf["entity_num"]
      rand = np.random.random(anum[-1]+1)
      area_color = rand[anum]
      meshes.append({"mesh": surf, "scalars": area_color})

The only reason for rand[anum] to show an index error is because the anum[-1]+1 is 1, meaning that in anum, the last element is zero. Because anum comes from surf["entity_num"] there should not be zero (one index based).

Several approaches here to increase robustness:

• Fix anum[-1] to be at least 1. I.e. np.random.random(max([anum[-1]+1,1])).
• Use max on anum, assuming that only the last element is zero. This might help us to "define" a bit more this random error. So I'm going for this.

[github-actions]

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[codecov]

Codecov Report

Merging #1691 (6535fff) into main (70c6b3b) will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1691      +/-   ##
==========================================
+ Coverage   85.18%   85.23%   +0.05%     
==========================================
  Files          45       45              
  Lines        7511     7506       -5     
==========================================
  Hits         6398     6398              
+ Misses       1113     1108       -5