output: #fixed code
                                  protected ASTNode verify(ParserContext pCtx, ASTNode tk) {
          if (tk.isDiscard() || (tk.fields & (ASTNode.OPERATOR | ASTNode.LITERAL)) != 0) return tk;
  
          if (verifying) {
              if (tk.isAssignment()) {
                  char[] assign = tk.getNameAsArray();
                  int c = 0;
                  while (c < assign.length && assign[c] != '=') c++;
  
                  String varName = new String(assign, 0, c++).trim();
  
                  if (isReservedWord(varName)) {
                      addFatalError("invalid assignment - variable name is a reserved keyword: " + varName);
                  }
  
                  ExpressionCompiler subCompiler =
                          new ExpressionCompiler(new String(assign, c, assign.length - c).trim());
  
                  subCompiler._compile();
  
                  pCtx.addVariable(varName, returnType = tk.getEgressType());
              }
              else if (tk.isIdentifier()) {
                  PropertyVerifier propVerifier = new PropertyVerifier(tk.getNameAsArray(), getParserContext());
                  pCtx.addInput(tk.getAbsoluteName(), returnType = propVerifier.analyze());
  
              }
          }
          return tk;
      }
input: #vulnerable code 
                                  protected ASTNode verify(ParserContext pCtx, ASTNode tk) {
          if (tk.isDiscard() || (tk.fields & (ASTNode.OPERATOR | ASTNode.LITERAL)) != 0) return tk;
  
          if (verifying) {
  
              if (tk.isAssignment()) {
                  char[] assign = tk.getNameAsArray();
                  int c = 0;
                  while (c < assign.length && assign[c] != '=') c++;
  
                  String varName = new String(assign, 0, c++).trim();
  
                  if (isReservedWord(varName)) {
                      addFatalError("invalid assignment - variable name is a reserved keyword: " + varName);
                  }
  
                  locals.add(varName);
  
                  ExpressionCompiler subCompiler =
                          new ExpressionCompiler(new String(assign, c, assign.length - c).trim());
  
                  subCompiler._compile();
  
                  inputs.addAll(subCompiler.getInputs());
  
                  pCtx.addVariable(varName, tk.getEgressType());
              }
              else if (tk.isIdentifier()) {
                  inputs.add(tk.getAbsoluteName());
  
                  PropertyVerifier propVerifier = new PropertyVerifier(tk.getNameAsArray(), getParserContext());
                  returnType = propVerifier.analyze();
  
                  inputs.addAll(propVerifier.getInputs());
              }
          }
  
          return tk;
      } 
                              #location 31 
                              #vulnerability type NULL_DEREFERENCE