#vulnerable code 
                                private static void writeSymJson(@NotNull Binding binding, JsonGenerator json) throws IOException {
        if (binding.start < 0) {
            return;
        }

        String name = binding.node.name;
        boolean isExported = !(
                Binding.Kind.VARIABLE == binding.kind ||
                        Binding.Kind.PARAMETER == binding.kind ||
                        Binding.Kind.SCOPE == binding.kind ||
                        Binding.Kind.ATTRIBUTE == binding.kind ||
                        (name != null && (name.length() == 0 || name.startsWith("lambda%"))));

        String path = binding.qname.replace("%20", ".");

        if (!seenDef.contains(path)) {
            seenDef.add(path);

            if (binding.kind == Binding.Kind.METHOD) {
                neMethods++;
            }
            if (binding.kind == Binding.Kind.CLASS) {
                neClass++;
            }

            json.writeStartObject();
            json.writeStringField("name", name);
            json.writeStringField("path", path);
            json.writeStringField("file", binding.file);
            json.writeNumberField("identStart", binding.start);
            json.writeNumberField("identEnd", binding.end);
            json.writeNumberField("defStart", binding.bodyStart);
            json.writeNumberField("defEnd", binding.bodyEnd);
            json.writeBooleanField("exported", isExported);
            json.writeStringField("kind", kindName(binding.kind));

            if (binding.kind == Binding.Kind.METHOD || binding.kind == Binding.Kind.CLASS_METHOD) {
                // get args expression
                String argExpr = null;
                Type t = binding.type;

                if (t.isUnionType()) {
                    t = t.asUnionType().firstUseful();
                }

                if (t != null && t.isFuncType()) {
                    Function func = t.asFuncType().func;
                    if (func != null) {
                        argExpr = func.getArgList();
                    }
                }

                String signature;
                if (argExpr == null) {
                    signature = "";
                } else if (argExpr.equals("()")) {
                    signature = "";
                } else {
                    signature = argExpr;
                }
                json.writeStringField("signature", signature);
            }


            String doc = binding.findDocString().value;
            if (doc != null) {
                json.writeStringField("docstring", doc);
            }

            json.writeEndObject();
        }
    } 
                            #location 65 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private static void writeSymJson(@NotNull Binding binding, JsonGenerator json) throws IOException {
        if (binding.start < 0) {
            return;
        }

        String name = binding.node.name;
        boolean isExported = !(
                Binding.Kind.VARIABLE == binding.kind ||
                        Binding.Kind.PARAMETER == binding.kind ||
                        Binding.Kind.SCOPE == binding.kind ||
                        Binding.Kind.ATTRIBUTE == binding.kind ||
                        (name != null && (name.length() == 0 || name.startsWith("lambda%"))));

        String path = binding.qname.replace("%20", ".");

        if (!seenDef.contains(path)) {
            seenDef.add(path);

            json.writeStartObject();
            json.writeStringField("name", name);
            json.writeStringField("path", path);
            json.writeStringField("file", binding.file);
            json.writeNumberField("identStart", binding.start);
            json.writeNumberField("identEnd", binding.end);
            json.writeNumberField("defStart", binding.bodyStart);
            json.writeNumberField("defEnd", binding.bodyEnd);
            json.writeBooleanField("exported", isExported);
            json.writeStringField("kind", kindName(binding.kind));

            if (binding.kind == Binding.Kind.METHOD || binding.kind == Binding.Kind.CLASS_METHOD) {
                // get args expression
                Type t = binding.type;

                if (t.isUnionType()) {
                    t = t.asUnionType().firstUseful();
                }

                if (t != null && t.isFuncType()) {
                    Function func = t.asFuncType().func;
                    if (func != null) {
                        String signature = func.getArgList();
                        if (!signature.equals("")) {
                            signature = "(" + signature + ")";
                        }
                        json.writeStringField("signature", signature);
                    }
                }
            }

            Str docstring = binding.findDocString();
            if (docstring != null) {
                json.writeStringField("docstring", docstring.value);
            }

            json.writeEndObject();
        }
    }