Never pass falsy value to date format

Closes #141

After adding TypeORM I had to remove the strict checking in TypeScript.
This leads to null errors such as this. Kind of annoying, but I think
the large reduction in code from adding TypeORM is worth it. We
shall see...

EditSet.tsx

@@ -162,7 +162,7 @@ export default function EditSet() {
           <AppInput
             label="Created"
             disabled
-            value={format(new Date(set.created), settings.date)}
+            value={format(new Date(set.created), settings.date || 'P')}
           />
         )}