Recently, the national security agency received a clue that a certain national defense and military industrial unit took the initiative to report. The person involved in the case, Zhang, took the initiative to report to this unit that while he was engaged in postdoctoral research abroad, he had established a paid consulting relationship with an overseas investment consulting company and leaked internal information related to my scientific research project to the other party. 经调查，国家安全机关最终决定依法不追究张某的法律责任。 到底是怎么回事？