fix: quicksearch searching by null throws error

The middleware automatically converts empty strings to null. We want to accept empty strings here for the search to work. Currently, the regex throws an error when a null is passed to it.

app/Http/Controllers/API/QuickSearchController.php

@@ -27,7 +27,7 @@ class QuickSearchController extends Controller
 {
     public function index(Request $request): \Illuminate\Http\JsonResponse
     {
-        $query = $request->input('query');
+        $query = $request->input('query', '');
 
         $filters = [
             'deleted_at IS NULL',