add missing new keyword

src/FFMpeg/Format/Dimension.php

@@ -33,7 +33,7 @@ class Dimension
     public function __construct($width, $height)
     {
         if ($width <= 0 || $height <= 0) {
-            throw InvalidArgumentException('Width and height should be positive integer');
+            throw new InvalidArgumentException('Width and height should be positive integer');
         }
 
         $this->width = (int) $width;