Can't open a page in Viewport if the page has been approved with Comala Workflows

Steps to reproduce:

1. Create a space and apply a workflow that features same space publishing feature,

2. approve one of the pages to achieve the state where the page can have an "approved" and "non-approved" states,

3. activate Scroll Viewport integration with Comala Workflows,

4. open a page from step #2 in Viewport

Expected result:
the page opens in Viewport

Actual result:
user sees a stacktrace instead of the page