The error message you quote applies to the <Done> exit of the Load Country Database action, warning that it has no type defined, while it should be of type Nothing. Note that the error should also appear while performing validation (which should occur by default when saving, see Window -> Preferences -> Tersus -> Validation).
Every trigger and exit (generically called slots) in the model must have a type defined (see the dataTypeId property in the Properties view.
There are various way in which a type can be set:
Thus, the easiest method to resolve the error is to drag a Nothing type from the palette over the <Done> exit. Other options would be:
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