I think the issue is when _endingMilesController.text might be null or contain unexpected values. A robust solution is to use double.tryParse() to safely convert the text to a double. If double.tryParse() returns null (meaning the conversion failed), assign a default value, such as null or 999999.

Try :

1. Parse using double.tryParse() on _endingMilesController.text.
2. Handle the null result by assigning your chosen default.