LateInitializationError: Field '_selectedItemIndex@25278355' has not been initialized.

[prateekmedia]

════════ Exception caught by widgets library ═══════════════════════════════════
The following LateError was thrown building CollapsibleSidebar(
dirty, dependencies: [_EffectiveTickerMode], state: 
_CollapsibleSidebarState#b9f65(ticker inactive)):

LateInitializationError: Field '_selectedItemIndex@25278355' has not been initialized.

This error is related to null safety and late initialization of _selectedItemIndex parameter.

[luimot]

I had the same Exception thrown and after reading some of the example code available, it seems that _selectedItemIndex is null until setting

isSelected: true

to a CollapsibleItem in the List of items