Drop `_recorded_property_dict` from XML on components

When a validated component is edited, mixin.component.RecordablePropertyMetaClass records the text_content property. This recorded property will be cleared afterwards if no errors are found, but this causes differences in business template XML for each component the first time they are edited.

This change is about removing the _recorded_property_dict when there are no property recorded, which leads to slightly smaller pickles (and business template XML, because they are also pickles).