Update Model.php

src/Grid/Model.php

@@ -535,7 +535,9 @@ class Model
             return;
         }
 
-        return $this->request->get($this->getPerPageName()) ?: $this->perPage;
+        $perPage =  $this->request->get($this->getPerPageName()) ?: $this->perPage;
+        if($perPage) return (int)$perPage;
+        return null;
     }
 
     /**