Fixed non string columns breaking model filter with collection driver (…

…#507)

* Added check for string

* Fixed styling

src/Engines/CollectionEngine.php

@@ -120,6 +120,10 @@ protected function searchModels(Builder $builder)
             foreach ($columns as $column) {
                 $attribute = $model->{$column};
 
+                if (! is_string($attribute)) {
+                    continue;
+                }
+
                 if (Str::contains(Str::lower($attribute), Str::lower($builder->query))) {
                     return true;
                 }