ValueChangedEvent not fired for ImageEncode-Event from Browser

[tobiaskahl]

Describe the bug
The ValueChangedEvent will not be fired, if private properties are updates.

Error
The if-statement of the following method is always false:
` // Used to sync the private variables (called after the frontend event has been
// fired)
private void updateImage(ImageEncode event) {
this.imageUri = event.getImage();
this.type = event.getType();
this.isEmpty = event.isEmpty();

if (!this.imageUri.equals(event.getImage())) {
  this.fireEvent(
      new ValueChangedEvent(
          event.getSource(), true, event.getImage(), event.getType(), event.isEmpty()));
}

}`
this.imageUri is set to the event-value in first line and compared afterwards.
The two values are always the same at this time.
Thie oldImageUri-Value has to be saved as local variable and then used in the if statement.