pyvista: SegFault when closing session after pyvista.plot

Describe the bug, what’s wrong, and what you expect:

After plotting and exiting a Python session, a segfault occurs. See output from bash below

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To Reproduce

(dev) ➜  pyvista git:(master) python
Python 3.7.3 | packaged by conda-forge | (default, Dec  6 2019, 08:36:57)
[Clang 9.0.0 (tags/RELEASE_900/final)] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyvista as pv
>>> pv.Sphere().plot()
[(1.014693063938463, 1.3721835511497151, 2.8672508897437536),
 (0.0, 0.0, 0.0),
 (-0.6903521188359678, -0.5264483112597669, 0.49625208069128485)]
>>> exit()
[1]    17751 segmentation fault  python
(dev) ➜  pyvista git:(master)

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System Information: Please run the following code wherever you are experiencing the bug and paste the output below. This report helps us track down bugs and it is critical to addressing your bug:

# Get system info
import pyvista as pv
print(pv.Report())

(On master branch)

--------------------------------------------------------------------------------
  Date: Wed Jan 22 10:52:07 2020 MST

            Darwin : OS
                12 : CPU(s)
            x86_64 : Machine
             64bit : Architecture
           32.0 GB : RAM
            Python : Environment
        GPU Vendor : ATI Technologies Inc.
      GPU Renderer : AMD Radeon Pro Vega 20 OpenGL Engine
       GPU Version : 4.1 ATI-3.4.19

  Python 3.7.3 | packaged by conda-forge | (default, Dec  6 2019, 08:36:57)
  [Clang 9.0.0 (tags/RELEASE_900/final)]

            0.23.0 : pyvista
             8.2.0 : vtk
            1.17.3 : numpy
             2.6.1 : imageio
             1.4.3 : appdirs
             0.5.0 : scooby
             3.1.2 : matplotlib
            5.12.3 : PyQt5
             7.6.1 : IPython
             1.0.0 : colorcet
               2.0 : cmocean
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