App crashes when browsing an app that has changed since last refresh

[sethuster]

When users try and explore a application tree, from a previously cached version of the application attached, PurpleUI will crash unexpectedly. This might go well with a fix for issue #19.

Steps to Reproduce:

1. Start PurpleUI and attach it to an application (LQP for example)
2. Browse through the application tree and get info on an element
3. In the attached application, make a change. Open a panel or do something significant
4. Attempt to browse the application tree in PurpleUI
5. Observe the crash, ZE CRASH!