When a signal is emitted from the C++ side due to a property being updated then it can trigger an onXXXChanged handler even if the component is not completed

When a signal is emitted from the C++ side due to a property being updated then it can trigger an onXXXChanged handler even if the component is not completed. It should only call this handler if the component is completed because otherwise it can trigger handling even though the property was just set the first time.