error when stop process before data_object is created

Traceback (most recent call last):
  File "/Users/ldam/Documents/GIT/sohstationviewer/sohstationviewer/view/main_window.py", line 897, in reset_flags
    if len(self.data_object.keys) > 1:
AttributeError: 'MainWindow' object has no attribute 'data_object'