The explicit check for undefined ensures that the value 0 of a
number property is taken from serialized elements.

The explicit check for undefined ensures that the value false of a
boolean property is taken from serialized elements.

This way the color-input element can read the color and show the correct 
preview.

To make it's purpose clearer.

Before the defaults were simply set on any field regardless of the 
passed object.

This keeps import cycles from happening.