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).

See merge request !1605