problem

The restriction to triton and aria theme did not respect other system default themes as triton. Therefore some users (which has changed the theme once and now has a custom user config entry) are resetted now to triton instead to the system default.

solution

Separate the systemdefault theme and the user chosen theme in two different configs, one on instance level one on user level. The user level has the defaults, default, triton, aria, where default points to the system default. The systemdefault has all possible values as defaults.