FATAL ERROR during battle

If your game crashes, please copy and paste the full error message below, or post a screenshot of it.

Please describe in as much detail as possible how to reproduce the bug or crash.

I was mid-battle and this came up. Last spell cast was Fury Swipes.

What operating system are you playing the game on? Windows, Mac OS, Android, iOS, or Playstation?
If it’s Playstation, please also state your region (NA or EU). If it’s a mobile device, please state the device’s model/brand (such as Nexus 5 or Samsung Galaxy Tab 4).

What game version are you playing? You can find the version number on the title screen in the lower left corner.