[BUG] undefined css variable used as tomselect active item background

[lovasoa]

Describe the bug

The builtin tabler-specific styling for Tom Select contains a reference to an undefined variable (--tblr-text-secondary-rgb) :

https://github.com/tabler/tabler/blob/v1.0.0-beta20/dist/css/tabler-vendors.css#L826-L829

Initially reported in lovasoa/SQLpage#297

How to reproduce

1. Go to https://jsfiddle.net/zbf2j3wr/
2. Click on select an option
3. press the arrow down key

expected result: you can visually identify which option is selected
actual result: no visual difference between the active option and the others

Screenshots

JSFiddle

https://jsfiddle.net/zbf2j3wr/