Fix dependency mismatch handling when popup has been closed

Using
Windows 10
Nuxeo Server 9.3 snapshot (2017-11-16)
MongoDB
JSF UI
Redis
BDE 2.0

In Studio

• Add a dependency in app def screen that is not installed on server yet
• Create a new doctype

In Nuxeo Server

• Trigger hot reload using BDE
• Close popup
• Wait for ~10 seconds
• Reopen popup

=> Dependency mismatch appears but package list is empty and clicking buttons has no effect anymore
=> Closing / reopening the popup brings the same screen, only workaround is to uninstall / reinstall the extension

Problem can't be reproduced if popup is kept open during hot reload.

Expected: packages list should be kept and buttons should remain functional