chore: fix errant 0 in output (#127)

Author: tstirrat15

src/components/FullPlayground.tsx

@@ -824,7 +824,8 @@ export function ThemedAppView(props: { datastore: DataStore }) {
               </div>
             )}
 
-            {currentItem?.kind &&
+            {/* NOTE: the kind here is an enum, so 0 will render. */}
+            {currentItem?.kind !== undefined &&
               [DataStoreItemKind.ASSERTIONS, DataStoreItemKind.EXPECTED_RELATIONS].includes(
                 currentItem.kind,
               ) && (