Party Assertion error

[Alpha 8 build 2083]
When I tried to access my party list about 2 hours into my latest game I got an Assertion failed error:

Message
Uncaught Error: Assertion failed: calling set on destroyed object
backtrace
line number
3865
char offset
filename
http://radiant/stonehearth/ui/root/js/libs/ember-1.8.1.js

After the error popped up I tried looking at my party list and found it empty. I saved and reloaded and it was fixed when the reload was finished.