Error on closing window

When closing down a window created with mlab, I get the following error
```
Traceback (most recent call last):
File "/Users/brey/miniconda3/envs/mayavi/lib/python3.7/site-packages/tvtk/pyface/ui/qt4/scene.py", line 60, in resizeEvent
self._scene._renwin.update_traits()
AttributeError: 'NoneType' object has no attribute 'update_traits'
Abort trap: 6
```
I have clean conda env with
```
conda install mayavi python=3.7
```
I have tried a couple of the mlab examples on the repo and I got the error all the time. I am on OS X.

My conda list is
```
apptools 4.5.0 py_0 conda-forge
bzip2 1.0.8 h0b31af3_2 conda-forge
ca-certificates 2020.4.5.1 hecc5488_0 conda-forge
certifi 2020.4.5.1 py37hc8dfbb8_0 conda-forge
configobj 5.0.6 py_0 conda-forge
curl 7.69.1 h2d98d24_0 conda-forge
dbus 1.13.6 h2f22bb5_0 conda-forge
envisage 4.9.2 py_0 conda-forge
expat 2.2.9 h4a8c4bd_2 conda-forge
freetype 2.10.2 h8da9a1a_0 conda-forge
future 0.18.2 py37hc8dfbb8_1 conda-forge
gettext 0.19.8.1 h46ab8bc_1002 conda-forge
glib 2.64.3 h577aef8_0 conda-forge
hdf4 4.2.13 h84186c3_1003 conda-forge
hdf5 1.10.6 nompi_h3e39495_100 conda-forge
icu 64.2 h6de7cb9_1 conda-forge
jpeg 9d h0b31af3_0 conda-forge
jsoncpp 1.8.4 ha1b3eb9_1002 conda-forge
krb5 1.17.1 h1752a42_0 conda-forge
libblas 3.8.0 16_openblas conda-forge
libcblas 3.8.0 16_openblas conda-forge
libclang 9.0.1 default_hf57f61e_0 conda-forge
libcurl 7.69.1 hc0b9707_0 conda-forge
libcxx 10.0.0 h1af66ff_2 conda-forge
libedit 3.1.20170329 hcfe32e1_1001 conda-forge
libffi 3.2.1 h4a8c4bd_1007 conda-forge
libgfortran 4.0.0 2 conda-forge
libiconv 1.15 h0b31af3_1006 conda-forge
liblapack 3.8.0 16_openblas conda-forge
libllvm9 9.0.1 h7475705_1 conda-forge
libnetcdf 4.7.4 nompi_ha11d67f_104 conda-forge
libopenblas 0.3.9 h3d69b6c_0 conda-forge
libpng 1.6.37 hbbe82c9_1 conda-forge
libpq 12.2 h489d428_1 conda-forge
libssh2 1.9.0 h39bdce6_2 conda-forge
libtiff 4.1.0 h2ae36a8_6 conda-forge
libwebp-base 1.1.0 h0b31af3_3 conda-forge
libxml2 2.9.10 h53d96d6_0 conda-forge
llvm-openmp 10.0.0 h28b9765_0 conda-forge
lz4-c 1.9.2 h4a8c4bd_1 conda-forge
mayavi 4.7.1 py37ha91d4f2_2 conda-forge
ncurses 6.1 h0a44026_1002 conda-forge
nspr 4.20 h0a44026_1000 conda-forge
nss 3.47 hc0980d9_0 conda-forge
numpy 1.18.4 py37h7687784_0 conda-forge
openssl 1.1.1g h0b31af3_0 conda-forge
pcre 8.44 h4a8c4bd_0 conda-forge
pip 20.1.1 py_1 conda-forge
pyface 6.1.2 py_0 conda-forge
pygments 2.6.1 py_0 conda-forge
pyqt 5.12.3 py37ha62fc16_3 conda-forge
pyqt5-sip 4.19.18 pypi_0 pypi
pyqtchart 5.12 pypi_0 pypi
pyqtwebengine 5.12.1 pypi_0 pypi
python 3.7.6 h90870a6_5_cpython conda-forge
python_abi 3.7 1_cp37m conda-forge
qt 5.12.5 h514805e_3 conda-forge
readline 8.0 hcfe32e1_0 conda-forge
setuptools 47.1.1 py37hc8dfbb8_0 conda-forge
six 1.15.0 pyh9f0ad1d_0 conda-forge
sqlite 3.30.1 h93121df_0 conda-forge
tbb 2019.9 ha1b3eb9_1 conda-forge
tk 8.6.10 hbbe82c9_0 conda-forge
traits 6.0.0 py37h9bfed18_1 conda-forge
traitsui 6.1.3 py_0 conda-forge
vtk 8.2.0 py37hd5eadda_218 conda-forge
wheel 0.34.2 py_1 conda-forge
xz 5.2.5 h0b31af3_0 conda-forge
zlib 1.2.11 h0b31af3_1006 conda-forge
zstd 1.4.4 h4b3e974_3 conda-forge
```