Image window freezes when you run PLNSOL

Describe the bug When you run mapdl.plnsol("U", "SUM"), the image is shown in a windows but you cannot close it and the script does not move from there.

To Reproduce Run the next command lines:

from ansys.mapdl.core import launch_mapdl 

mapdl = launch_mapdl(loglevel="WARN") 
mapdl.prep7() 
mapdl.cdread("comb", "disc_pad_mode", "cdb", "", "")  # Read disc_pad_model.cdb file

mapdl.allsel("all")
mapdl.run("/SOLU")
mapdl.antype("MODAL")  # Perform modal solve
mapdl.nropt("UNSYM")  # To generate non symmetric
mapdl.cmsel("S", "C1_R")  # Select the target elements of the disc
mapdl.cmsel("A", "C2_R")
mapdl.cm("E_ROTOR", "ELEM")  # Form a component named E_ROTOR with the selected target elements
mapdl.allsel("ALL")
mapdl.cmrotate("E_ROTOR", "", "", 2)  # Rotate the selected element along global Z using CMROTATE command
mapdl.modopt("UNSYM", 30)  # Use UNSYM to extract 30 modes
mapdl.mxpand(30)  # Expand 30 modes, do not calculate element results
mapdl.solve()
mapdl.finish()

mapdl.run("/post1")
mapdl.run("/out,")
mapdl.set("list")
mapdl.set(1, 21)
mapdl.plnsol("u", "sum") #This will freeze the plot window. I could just kill the process with Ctrl+C

You can download the CDB file from: https://github.com/pyansys/example-data/blob/master/tech_demos/td-1/disc_pad_model.cdb

Expected behavior The plot window should be able to be closed.

System Information:

• OS: Windows 10
• Ansys version 2020R2
• PyMAPDL version 0.59 dev0

Additional context Add any other context about the problem here.

PyMAPDL report

-------------------------------------------------------------------------------
PyMAPDL Software and Environment Report
-------------------------------------------------------------------------------
  Date: Mon Oct 25 11:17:06 2021 Romance Daylight Time

                OS : Windows
            CPU(s) : 16
           Machine : AMD64
      Architecture : 64bit
       Environment : Python
             Intel : GPU Vendor
Intel(R) UHD Graphics : GPU Renderer
4.5.0 - Build 30.0.100.9864 : GPU Version

  Python 3.8.11 (default, Aug  6 2021, 09:57:55) [MSC v.1916 64 bit (AMD64)]

        matplotlib : 3.4.3
             numpy : 1.21.2
           pyvista : 0.31.3
           appdirs : 1.4.4
              tqdm : 4.62.2
            pyiges : 0.2.0
             scipy : 1.7.1
              grpc : 1.39.0
  ansys.grpc.mapdl : 0.4.0
ansys.mapdl.reader : 0.51.3
   google.protobuf : 3.17.3
       ansys_corba : Version unknown
-------------------------------------------------------------------------------

Ansys Installation
******************
Version   Location
------------------
212       C:\Program Files\ANSYS Inc\v212


Ansys Environment Variables
***************************
ANSYS212_DIR                   C:\Program Files\ANSYS Inc\v212\ANSYS
ANSYSLIC_DIR                   C:\Program Files\ANSYS Inc\Shared Files\Licensing
AWP_LOCALE212                  en-us
AWP_ROOT212                    C:\Program Files\ANSYS Inc\v212
CADOE_LIBDIR212                C:\Program Files\ANSYS Inc\v212\CommonFiles\Language\en-us

[germa89]

This was finally fixed by installing pyqt5.

python pip install pyqt5

[germa89]

This is due to #934