seq.get函数使用问题

目前seq.get函数，当传入null的集合时会抛出异常，特别是在seq.get(seq.get(col,a),b)类似这样的场景中，判空操作很麻烦
。扩展下场景，是否考虑增加全局配置对异常的控制，可以控制异常类似这样的异常返回nil，类似jsonpath的操作

Start by locating the seq.get entry point and reviewing how null collections currently fail, especially in nested calls such as seq.get(seq.get(col,a),b). Clarify whether the desired behavior is always returning nil or is controlled by a global setting, then define the expected behavior and tests for both direct and nested calls.

Written by the indexing model from the issue text.