add eloquent check

Author: Brian Dillingham

src/AttachMany.php

@@ -41,14 +41,16 @@ public function __construct($name, $attribute = null, $resource = null)
         $this->resourceName = $resource::uriKey();
         $this->manyToManyRelationship = $this->attribute;
 
-        $this->fillUsing(function($request, $model, $attribute, $requestAttribute){
-            $model::saved(function($model) use($attribute, $request) {
-                $model->$attribute()->sync(
-                    json_decode($request->$attribute, true)
-                );
-            });
-
-            unset($request->$attribute);
+        $this->fillUsing(function($request, $model, $attribute, $requestAttribute) use($resource) {
+            if(is_subclass_of($model, 'Illuminate\Database\Eloquent\Model')) {
+                $model::saved(function($model) use($attribute, $request) {
+                    $model->$attribute()->sync(
+                        json_decode($request->$attribute, true)
+                    );
+                });
+
+                unset($request->$attribute);
+            }
         });
     }