Can't create device group

I recently had some problems with my hub randomly crashing every few minutes. In an effort to get it back to a stable state, I removed a bunch of apps and devices from the hub. Once of the apps I removed is the built-in Groups and Scenes app.

The hub is stable again, so I've been trying to return to the level of automation I had prior to the instability. I have re-added a couple of apps and rules and such. I re-added the Groups and Scenes app, but I can't create any groups because I get the following error: "Error: Cannot invoke method hasCapability() on null object"

I'm running version on hardware Rev C-4.

I have tried looking for similar topics a few times over the past couple of weeks. So far I haven't discovered any. Anyone have any suggestions for how to fix this myself?

Thanks in advance!