Do not assume the $rootScope.current_folder will exist.

I still haven't decided what solution will I adopt to tell the angularjs scope that a folder has been selected for reading.
Show/hide the entries list and start page based on whether the angularjs model says a feed is currently selected for reading.
When the start link in the sidebar is clicked, the global currently selected feed is set to null.

This is part of the transition to angularJS: instead of registering event handlers to change the DOM (triggering classes or whatnot), ng- attributes are added that call methods in the controller, which set model values in the scope. Then visual properties in the page are made dependant on those model values.

This way the DOM is not directly changed by event handler. Rather event handlers change values in the model, and that triggers changes in the DOM automatically.
Mark feeds as active/inactive in the sidebar based on the angularjs model.
When angularJS unsubscribes a feed, the unread entries count in the sidebar are updated and the folder deleted if empty.
The unsubscribe popup is displayed with bootstrap data- attributes, instead of registering a handler function for the button onClick event.