fix: protect taurusgui against lack of PyQtWebEngine

Manual panel's widget is None when PyQtWebEngine is not installed. Avoid exception on closing GUI by only propagating the closeEvent to the panel's widget when it exists.

MainThread     ERROR    2022-01-10 14:03:58,500 LogExceptHook: Unhandled exception:
Traceback (most recent call last):
  File "c:\users\vagrant\appdata\local\programs\python\python38\lib\site-packages\taurus\qt\qtgui\taurusgui\taurusgui.py", line 426, in closeEvent
    panel.widget().closeEvent(event)
AttributeError: 'NoneType' object has no attribute 'closeEvent'

added bug label

Looks like there are some problems with taurus/test/test_import.py, @c-p maybe you could help, please?

changed milestone to %Jan22

The changes LGTM.

Regarding the test failing, I suspect a regression introduced in a recent build of the taurus-docker:conda-3.{7,8,9} images. I 'll investigate

I confirm my suspicion about the regression. If triggering the CI on the develop branch now fails when it uses the latest images (version -20220109) but it works fine if pinning the previous version (version -20220102)

I'll see if I can quickly fix the regression and, if not, I'll revert the latest images to version -20220102

mentioned in commit 30c59fe6

merged

oh! I merged accidentally (I wanted to wait until I fixed the CI regression) but anyway, I think it is ok and safe to merge

Regarding the conda images regression, it is now fixed with this commit in taurus-docker.

For some reason the base conda images on which we base ours stopped installing a needed library.

In any case this makes clear that it would be very convenient to do a test with the auto-generated images before pushing them to the production registry. I'll see if I can do something quick about that.

mentioned in issue #1287 (closed)