Configuration Table Editor does not display if linked table empty

[lostcarpark]

The configuration table editor uses foreign keys to populate reference table drop-downs.
However, if a referenced (parent) table is empty, the linking (child) table will not display in the configuration table editor.
This is fairly reasonable behaviour, since it won't be possible to add rows to the child table until the parent table is populated. However, currently no error message is displayed, so it isn't obvious why the table isn't displaying.
This problem could be largely avoided by ensuring there is at least one sample row in all referenced tables. However, in the long term we should try adding logic to display a message such as "You cannot edit table X until table Y has been populated."