An internal error occurred during: "Hg subscriber data update".

This happens after pushing pending changes to the remote server.

java.lang.NullPointerException: Cannot invoke "java.util.List.size()" because "members" is null
	at com.vectrace.MercurialEclipse.team.cache.MercurialStatusCache.checkForConflict(MercurialStatusCache.java:1118)
	at com.vectrace.MercurialEclipse.team.cache.MercurialStatusCache.refreshStatus(MercurialStatusCache.java:913)
	at com.vectrace.MercurialEclipse.synchronize.MercurialSynchronizeSubscriber.refresh(MercurialSynchronizeSubscriber.java:473)
	at com.vectrace.MercurialEclipse.synchronize.HgSubscriberScopeManager$UpdateDataJob.run(HgSubscriberScopeManager.java:257)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information