Realm crashes upon trying to enter configuration menu

Whenever either 'configuration' button is clicked for a realm, screen flashes 'saving world' and crashes to launcher. Displays error code  " The game crashed whilst rendering screen
Error: java.lang.NullPointerException: Cannot invoke "java.awt.image.BufferedImage.getWidth()" because "☃" is null
Exit Code: -1 "

 

Crash log attached. Issue happens on two different machines.