output: #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();
          }
      }
input: #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