Failed automatic object data conversion during a property rename results in data loss

(See the 3 attached xar files)

Steps to reproduce:

1. Import class-date.xar
2. Import data-date.xar
3. Go to Accounts/TestInstance/?editor=object and see the test property of type date with a date value
4. Import class-string.xar (thus triggering a conversion of the test property from date to string)
5. Go to Accounts/TestInstance/?editor=object and see the test property of type string with a successfully converted string value
6. Import class-data.xar (thus triggering a conversion of the test property from string to date)
7. Go to Accounts/TestInstance/?editor=object and see the test property of type date with a failed conversion and an empty value, thus losing the data.
   

Expected result:
If the conversion fails, the old data should be preserved as a deprecated property value stored in the object, just like it happens when you manually remove and then add a property with the same name (i.e. manually changing the type of a property).