#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
#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;
    }