[FIX] Tree Viewer: check if there is selected class value

[jerneju]

Issue

Tree Viewer crashes when Target Class combo selected index number is higher than actual number of class values.
https://sentry.io/biolab/orange3/issues/205702715/

Description of changes

Includes

• Code changes
• Tests
• Documentation

[jerneju]

https://sentry.io/biolab/orange3/issues/205702715/

[janezd]

This is a patch, not a fix. :)

The combo should not have had an invalid value in the first place. I guess you should discover why this occurred and fix the problem there.

[codecov-io]

Codecov Report

Merging #2224 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2224      +/-   ##
==========================================
+ Coverage   72.49%   72.49%   +<.01%     
==========================================
  Files         319      319              
  Lines       55210    55211       +1     
==========================================
+ Hits        40024    40025       +1     
  Misses      15186    15186

[janezd]

This is a patch, not a fix. :)

The combo should not have had an invalid value in the first place. I guess you should discover why this occurred and fix the problem there.

[jerneju]

Now I fixed it in another way.

[lanzagar]

Does not fix the problem for me.
Also, there are now two consecutive calls to openContext.

[janezd]

Now I fixed it in another way.

Where is this other fix? Did you forget to push?

[jerneju]

Where is this other fix? Did you forget to push?

Changed it back.

[janezd]

I don't get it. :) What is the state of this PR now? Should we just close it since it doesn't fix the problem in the right way and it doesn't contain any code that would be useful in the actual fix?

If we merge this as a "temporary fix", we nobody will remember to remove it after the actual fix ... and we have too much of such dead code already. :)

[janezd]

I thought that you would have to call self.color_combo.setCurrentIndex(self.target_class_index) after openContext, but setup_scene calls activate_loaded_settings which in turn calls the combo's setCurrentIndex. Knowing this, even the existing call self.color_combo.setCurrentIndex(self.target_class_index) is actually redundant ... but leave it as it is.