Hi,
it seems that you have to update your included files for the Envato WordPress Toolkit.
File: dante > includes > envato-wordpress-toolkit-library > class-envato-wordpress-theme-upgrader.php in line 308 reads
public function upgrade( $theme, $package ) {
instead of
public function upgrade( $theme, $package = array() ) {
as I could read in https://github.com/envato/envato-wordpress-toolkit/commit/c5a8f6d5441fd07dea4ca4a15f6236c097dd5194
Could you please verify this and update your files? A nasty error occurs when your theme is installed and for example the Bucket theme (http://themeforest.net/item/bucket-a-digital-magazine-style-wordpress-theme/6107209). This is especially nasty in a Multi-Site setup.
Thanks.