Special case empty string in lib/stringutil.StringDeduplicator.
Special case empty string in lib/stringutil.StringDeduplicator.

rgooch/Dominator,Symantec/Dominator,Symantec/Dominator,keep94/Dominator,Symantec/Dominator,rgooch/Dominator,keep94/Dominator,rgooch/Dominator,keep94/Dominator