fix variable name

Author: reb-ddm

core/KaSa_rep/reachability_analysis/analyzer_headers.ml

@@ -420,7 +420,7 @@ module AbstractWSMap (MapT : Map_wrapper.S_with_logs) = struct
             abstract_away_working_set_vars parameters error bdu_handler mvbdu
               working_set_mvbdu working_set_guards_hcons
           in
-          let error', current_working_set =
+          let error, current_working_set =
             MapT.Map.add parameters error rule_id mvbdu current_working_set
           in
           current_working_set, bdu_handler, error)