PointAnnotation disappear on update [Example app]

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In example app point_annotation page.

When I try and update PointAnnotation as per below code in example app then PointAnnotation disappears.

```
class AnnotationClickListener extends OnPointAnnotationClickListener {
AnnotationClickListener(this.pointAnnotationManager);

final PointAnnotationManager pointAnnotationManager;
@override
void onPointAnnotationClick(PointAnnotation annotation) async {
print("onAnnotationClick, id: ${annotation.id}");
if (annotation.textField == null) {
annotation.textField = "Test data";
annotation.textOffset = [0.0, -2.0];
annotation.textColor = Colors.red.value;
annotation.iconSize = 1.3;
annotation.iconOffset = [0.0, -5.0];
} else {
annotation.textField = null;
}
await pointAnnotationManager.update(annotation);
}
}
```

What i am trying to do here is if no text is being displayed then show text, if text is displayed then hide text.

Text show and hide works fine, but it also hide marker icon.

Start with the point_annotation page in the example app and reproduce the issue using the shown AnnotationClickListener and PointAnnotationManager.update call. Check why updating text and offsets also removes the marker icon, then verify that toggling the text leaves the icon visible in both states.

Written by the indexing model from the issue text.