The method '>=' was called on null.

Flutter - The getter 'length' was called on null, punkteanzahl_teamEins is only declared. But not initialized. So it is throwing null error. You should assign value to punkteanzahl_teamEins as Unhandled Exception: NoSuchMethodError: The getter 'id' was called on null. Receiver: null Tried calling: id 'The getter 'uid' was called on null' in flutter. 1. Additional reading

In my case : one of my variables were not intialised i.e double _bmi = 0;