The argument type 'Null' can't be assigned to the parameter type 'Offset'.

[ramseena-12]

Describe the bug
onPanEnd: (DragEndDetails details) {
setState(() {
_points.add(null);
});
},

in this -point.add(null); is giving the error the argument type null can't be assigned to the parameter type 'offset'

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Version [e.g. 22]

Additional context
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