Fix broken activity delete action, hide discussion on empty progress page

[MiroDojkic]

This PR:

• fixes broken activity delete action (#799)
• state is hydrated with a single SSE after bulk activity update; previously SSE was sent per item
• discussion is hidden in the progress page's sidebar when there's no selected activity

⚠️ Issue was caused by Sequelize's individualHooks flag in the model methods. When used, it loads instances with the appropriate scopes before running the update query. In this case, it caused the bug which would assign included model's alias (from the default scope) to update query's column.

:mag: QA note:

This change affects functionalities that save data to the server (creating and updating elements, repositories, etc.)

[kjuej]

@MiroDojkic @underscope Seems to be functioning as expected!