Dereference of a possibly null reference.

Non-nullable field '_selectedTheme' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Converting null literal or possible null value to non-nullable type.

Nullability of reference types in type of parameter 'sender' of 'void MainWindow.Caret_PositionChanged(object sender, EventArgs e)' doesn't match the target delegate 'EventHandler' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'sender' of 'void MainWindow.TextMateInstallationOnAppliedTheme(object sender, Installation e)' doesn't match the target delegate 'EventHandler<TextMate.Installation>' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'sender' of 'void MainWindow.SyntaxModeCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)' doesn't match the target delegate 'EventHandler<SelectionChangedEventArgs>' (possibly because of nullability attributes).

Non-nullable field '_foldingManager' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field '_completionWindow' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field '_insightWindow' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.