output: #fixed code
                                  @Nullable
      public String extendPath(@NotNull String name) {
          if (name.endsWith(".py")) {
              name = Util.moduleNameFor(name);
          }
  
          if (path.equals("")) {
              return name;
          }
  
          String sep;
          switch (scopeType) {
              case MODULE:
              case CLASS:
              case INSTANCE:
              case SCOPE:
                  sep = ".";
                  break;
              case FUNCTION:
                  sep = "@";
                  break;
              default:
                  Util.msg("unsupported context for extendPath: " + scopeType);
                  return path;
          }
  
          return path + sep + name;
      }
input: #vulnerable code 
                                  @Nullable
      public String extendPath(@NotNull String name) {
          if (name.endsWith(".py")) {
              name = Util.moduleNameFor(name);
          }
          if (path.equals("")) {
              return name;
          }
          String sep;
          switch (scopeType) {
              case MODULE:
              case CLASS:
              case INSTANCE:
              case SCOPE:
                  sep = ".";
                  break;
              case FUNCTION:
                  sep = "&";
                  break;
              default:
                  System.err.println("unsupported context for extendPath: " + scopeType);
                  return path;
          }
          return path + sep + name;
      } 
                              #location 6 
                              #vulnerability type NULL_DEREFERENCE