Added a missing change from a header.

src/ast/analysis/Aggregate.h

@@ -50,7 +50,7 @@ std::set<std::string> getVariablesOutsideAggregate(const Clause& clause, const A
  *  Find a new relation name. I use this when I create new relations either for
  *  aggregate bodies or singleton aggregates.
  **/
-std::string findUniqueRelationName(const Program& program, std::string base);
+std::string findUniqueRelationName(const Program& program, const std::string& base);
 /**
  * Find a variable name using base to form a string like base1
  * Use this when you need to limit the scope of a variable to the inside of an aggregate.