dataset image page bars don't update after filtering (by subfolder or annotated)

[felixdollack]

I noticed that the page bars are not updated when selecting a subfolder or filtering images (e.g Show annotated). It is not directly related to issue #320 but still somewhat similar.

[felixdollack]

The text in the sidebar shows correctly how many pages there are. Also, the page bar updates to the correct count if I go back up from a subfolder by clicking on the breadcrumb link.