fix corner case in collapse_vars (#5390)

fixes #5389

lib/compress.js

@@ -3269,7 +3269,7 @@ Compressor.prototype.compress = function(node) {
                 if (def.scope.resolve() !== scope) return true;
                 if (modify_toplevel && compressor.exposed(def)) return true;
                 return !all(def.references, function(ref) {
-                    return ref.scope.resolve() === scope;
+                    return ref.scope.resolve(true) === scope;
                 });
             }