Set protected static $sizes default value - array(). Correct to getting sizes use with static::

Image.class.php

@@ -10,7 +10,7 @@ class Image extends File
     public $original_filename;
     public $variants = array();
 
-    protected static $sizes;
+    protected static $sizes = array();
 
     /**
      * @param $class string
@@ -31,11 +31,16 @@ class Image extends File
 
     public function getSizes()
     {
-        return self::$sizes;
+        return static::$sizes;
     }
 
     public function getVariant($size)
     {
         return parent::getImageVariant($size);
     }
+
+    public function getIsNoEmpty()
+    {
+        return (bool) $this->size;
+    }
 }