force display column to be chosen when uploading csv

packages/builder/src/components/backend/TableNavigator/modals/CreateTableModal.svelte

@@ -105,7 +105,10 @@
   title="Create Table"
   confirmText="Create"
   onConfirm={saveTable}
-  disabled={error || !name || (rows.length && !allValid)}
+  disabled={error ||
+    !name ||
+    (rows.length && !allValid) ||
+    displayColumn == null}
 >
   <Input
     thin