brigadier nullable fix

app/Http/Controllers/Controller.php

@@ -72,7 +72,7 @@ class Controller extends BaseController
         foreach ($columns as $column) {
 
             $uniqueValues = $model::query()->distinct()->get($column)->pluck($column)->toArray();
-            if($uniqueValues[0] == null) {
+            if(isset($uniqueValues) && ($uniqueValues[0] == null)) {
                 $uniqueValues = [];
             }
             $result = [];