Invert condition: we should ignore empty crossrefs rather than non-empty ones for cite key changes. 
Invert condition: we should ignore empty crossrefs rather than non-empty ones for cite key changes. 

JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim