#158 ghost objects in recently_destroyed

[Michele Gubian]

e.g. when loading and staging IA you get the following recently_destroyed:
ANSWER: <object value="(parameter_store as_pattern)">
ANSWER: <object value="((::0x4ae58c8 parameters) as_pattern)">
ANSWER: <object value="((::0x4ae58c8 parameters) colname_dimensions)">
ANSWER: <object value="((::0x4ae58c8 parameters) colnames)">
ANSWER: <object value="((::0x4ae7a80 default_observer) colname_dimensions)">
ANSWER: <object value="((::0x4ae7a80 default_observer) colnames)">
ANSWER: <object value="::0x4b13ec0">
ANSWER: <object value="(model_impl parameters)">
ANSWER: <object value="(trial_impl default_observer)">

but none of them appears in created or modified.
The GUI is protected against this, but still it's not consistent at lazynut shell level.

</object></object></object></object></object></object></object></object></object>