Make #postload:package: on BaselineOfIDE set PharoLightTheme as current again

[Rinzwind]

This pull request makes #postload:package: on BaselineOfIDE set PharoLightTheme as current again to be consistent with it being the default (see issue #16797).

[demarey]

Thank you for this contribution. I don't think it is the right fix. The choice was done to adopt dark blue theme as default theme in Pharo 13.

I think the problem should be fixed in the settings browser. You mentionned

theme saving gets filtered out in #store on SettingsStonWriter because ‘Pharo Light’ is the default value.

Probably the default value should become dark blue in Pharo 13. And you're right that default theme should only be defined in one place.

[Rinzwind]

@jecisc Could you maybe extend the changes of pull request #16777 to correctly set the theme as the default then?

[jecisc]

https://github.com/pharo-project/pharo/pull/17087

[Rinzwind]

Thanks! Saving ‘Pharo Light’ for ‘User interface theme’ to disk works now.