Details entered when a contributor makes a contribution as a guest overwrites his previously stored information

This is a problem that occurs when contribution pages allow guest contributions and where the contribution page has included profiles that personal contact details like name and address.

As the person is not logged in while making contribution, all these fields will be empty by default.

If the name, address etc. fields are not required fields, the contributor may leave them blank.

Any information we may already have about this contributor in the CRM database (as linked by the email address he provides) will be replaced by this blank information so we can potentially lose name and address information due to this bug.