Fix "null" shown above import options

Rows needing review passed a null to the DOM's native append(), which
prints it as the text "null".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/static/js/import.js

@@ -201,8 +201,9 @@ export function openImport({ list, cat, onListChange, onDone }) {
         e.open = true;
         rerender(e);
       });
-      li.append(e.error ? h("p", { class: "small muted" }, e.error) : null,
+      // Native append() would print a null as the text "null".
-        h("div", { class: "import-opts" }, ...opts), again);
+      if (e.error) li.append(h("p", { class: "small muted" }, e.error));
+      li.append(h("div", { class: "import-opts" }, ...opts), again);
       return li;
     }