Preview button in toolbar indicates variant filters even if there is none.

To reproduce:

1. Open/create a project that has variant groups and tags.
2. Open the variant tag panel from the toolbar and apply one or more tags.
3. Now the preview button in the toolbar changes appearance to indicate that variant tags are in use for preview.
4. Open another project that does not have any variant groups or tags.
5. The preview button still indicates that variant tags are in use for the preview.