Paging to the next page doesn't work after all the items in the current page are deleted

[Kahou Lei]

I was not able to page to the next page after I delete all the instance of the current page.

Steps to reproduce:

1. In the user settings, set the Item per page as 3.
2. On the project -> Instance page, launch 6 instances.
3. You should see 3 instances per page in the instance table.
4. On the first page, delete all the instance at once.
5. After all the instances are deleted, click the "Next" link.
6. You should see an error saying that it cannot page to the next page (Unable to retrieve instance).

[Matt Fischer (mfisch)]

This also occurs if you delete the last item at the bottom of the page that's used as a pagination marker, you don't need to delete all of them.