Fix #701 Preferable default theme

[KitaitiMakoto]

This patch fixes #701 .

The issue occurs because form value of email is empty string "" when user selects "Default theme" and it is set as preferred theme name. There's no theme named "", so any theme is not applied. By setting NULL to users.preferred_theme when "Default theme" is selected, instance theme is used as the user's preferred theme.

I used Diesel's #[changeset_options(treat_none_as_null="true")] attribute on User model. This may not be preferred but save_changes doesn't have option to set NULL sometimes and keep current value otherwise(See http://diesel.rs/guides/all-about-updates/ . It says "Diesel doesn't currently provide a way to explicitly assign a field to its default value"). This is the reason why I used that attribute, but it may have too wide inpact. Could you consider?

[codecov]

Codecov Report

Merging #746 into master will not change coverage by %.
The diff coverage is 0.00%.

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[elegaanz]

I did a quick check to see if it could impact something else, but it looks like it is safe. Thanks for contributing!

[elegaanz]

Woops, forgot to approve

[KitaitiMakoto]

Thank you for merging!

[verymilan]

Sadly a new user of mine still just ran into missing CSS on 0.5.0 :(

[KitaitiMakoto]

@verymilan Can you re-save configuration again, please?

[verymilan]

I am not sure what you mean, but as usual, i have made them selecting a theme and save, which was fixing their issue as always

[KitaitiMakoto]

Sorry for my poor English. What I did mean is...

Can you have your users select "Default theme" and save it? It might be fix the issue?

Under the hood, their current theme is saved as empty string "" but re-saving theme makes it NULL. And then default theme is applied.

[verymilan]

Yes, i know, and this is how we did it - i was just expecting assuming that this workaround wasn't needed anymore.

[KitaitiMakoto]

Ah, sorry, I missed your point.

i was just expecting assuming that this workaround wasn't needed anymore.

Yes, your realization is correct.