Image API PS 1.7.6.1 ?

[PrestaFrShop]

Hello i have a question i want get images from api, all apis work like products infos etc but when i test for images

https://mysite.com/api/images/products?output_format=JSON            

 Undefined index: objectsNodeName (\/public_html\/classes\/webservice\/WebserviceOutputJSON.php, line 127)"}

but https://mysite.com/api/images/products    it s ok but i want json format

Can you help me

Thanks