output: #fixed code
                                FunctionTypeBuilder(String fnName, AbstractCompiler compiler,
        Node errorRoot, String sourceName, Scope scope) {
      Preconditions.checkNotNull(errorRoot);
  
      this.fnName = fnName == null ? "" : fnName;
      this.codingConvention = compiler.getCodingConvention();
      this.typeRegistry = compiler.getTypeRegistry();
      this.errorRoot = errorRoot;
      this.sourceName = sourceName;
      this.compiler = compiler;
      this.scope = scope;
    }
input: #vulnerable code 
                                FunctionTypeBuilder inferThisType(JSDocInfo info,
        @Nullable Node owner) {
      ObjectType maybeThisType = null;
      if (info != null && info.hasThisType()) {
        maybeThisType = ObjectType.cast(
            info.getThisType().evaluate(scope, typeRegistry));
      }
      if (maybeThisType != null) {
        thisType = maybeThisType;
        thisType.setValidator(new ThisTypeValidator());
      } else if (owner != null &&
                 (info == null || !info.hasType())) {
        // If the function is of the form:
        // x.prototype.y = function() {}
        // then we can assume "x" is the @this type. On the other hand,
        // if it's of the form:
        // /** @type {Function} */ x.prototype.y;
        // then we should not give it a @this type.
        String ownerTypeName = owner.getQualifiedName();
        ObjectType ownerType = ObjectType.cast(
            typeRegistry.getForgivingType(
                scope, ownerTypeName, sourceName,
                owner.getLineno(), owner.getCharno()));
        if (ownerType != null) {
          thisType = ownerType;
        }
      }
  
      return this;
    } 
                              #location 21 
                              #vulnerability type NULL_DEREFERENCE