Test passing baseline comparison with empty render view

Description

Some tests, at least pvcs.CompositeGlyphTree (and pvcrs version) pass from ctest point of view but produce an empty render view, while baseline is not empty.

Note that the information panel shows 6 points and 0 cells.

expected baseline:

So 2 issues here:

1. Why is the output empty?
2. Why does the testing framework not handle it?

Steps to reproduce

With tests enabled:

• ctest -R CompositeGly -VV -N to get the actual command line to run.
• Remove the --exit to keep the paraview application at the end. Command is something like that

/home/nicolas/ParaView/branch3/build/bin/smTestDriver-pv5.12 "--enable-bt" "--server" "/home/nicolas/ParaView/branch3/build/bin/pvserver" "--enable-bt" "--client" "/home/nicolas/ParaView/branch3/build/bin/paraview" "--enable-bt" "--test-script=/home/nicolas/ParaView/branch3/Clients/ParaView/Testing/XML/CompositeGlyphTree.xml" "--test-directory=/home/nicolas/ParaView/branch3/build/Testing/Temporary" "--test-baseline=/home/nicolas/ParaView/branch3/build/ExternalData/Clients/ParaView/Testing/Data/Baseline/CompositeGlyphTree.png" "--data-directory=/home/nicolas/ParaView/branch3/build/ExternalData" "--dr"

• Run it.

vtkSMTestDriver: starting process client
-------------- client output --------------
Process started
vtkSMTestDriver: client successfully started.
-------------- server output --------------
Client connected.
-------------- client output --------------
Process started
Playing: /home/nicolas/ParaView/branch3/Clients/ParaView/Testing/XML/CompositeGlyphTree.xml
(   6.272s) [paraview        ]vtkOpenGLGlyph3DMapper.:372    ERR| vtkOpenGLGlyph3DMapper (0x5e7d44ad1640): UseSourceTableTree is true, but the source dataset is not a vtkDataObjectTree.
(   6.307s) [paraview        ]vtkOpenGLGlyph3DMapper.:372    ERR| vtkOpenGLGlyph3DMapper (0x5e7d44ad1640): UseSourceTableTree is true, but the source dataset is not a vtkDataObjectTree.
(   6.355s) [paraview        ]vtkOpenGLGlyph3DMapper.:372    ERR| vtkOpenGLGlyph3DMapper (0x5e7d44ad1640): UseSourceTableTree is true, but the source dataset is not a vtkDataObjectTree.
debug: In ../ThirdParty/QtTesting/vtkqttesting/pqTestUtility.cxx, line 297
debug: Test  "CompositeGlyphTree.xml" is finished. Success =  true
(   6.369s) [paraview        ]vtkOpenGLGlyph3DMapper.:372    ERR| vtkOpenGLGlyph3DMapper (0x5e7d44ad1640): UseSourceTableTree is true, but the source dataset is not a vtkDataObjectTree.
(   6.376s) [paraview        ]         vtkTesting.cxx:780   WARN| Environment variable VTK_TESTING_IMAGE_COMPARE_METHOD is not set.
(   6.376s) [paraview        ]         vtkTesting.cxx:787   INFO| Using LEGACY_VALID image comparison method.
(   6.376s) [paraview        ]         vtkTesting.cxx:864   INFO| Comparing baselines using the default image baseline.
(   8.067s) [paraview        ]vtkOpenGLGlyph3DMapper.:372    ERR| vtkOpenGLGlyph3DMapper (0x5e7d44ad1640): UseSourceTableTree is true, but the source dataset is not a vtkDataObjectTree.

Configuration

• Operating system and version: archlinux
• ParaView executable and version: paraview master
• ParaView configuration: client-server mode only.