stack property Null safety
The stack trace from where the exception was thrown (as opposed to where it was caught).
StackTrace objects are opaque except for their toString function.
If this field is not null, then the stackFilter callback, if any, will be called with the result of calling toString on this object and splitting that result on line breaks. If there's no stackFilter callback, then FlutterError.defaultStackFilter is used instead. That function expects the stack to be in the format used by StackTrace.toString.
final StackTrace? stack;