SyntaxError: Unexpected token < in JSON at position 0 and some error

Hi All
Our OP version is 3.0.2
Got error when upload image via filemanager.

SyntaxError: Unexpected token < in JSON at position 0
Parser error
SyntaxError: JSON.parse Error : Invalid character at position:1 parsererror


Screenshot :
http://nimb.ws/TpD190

Is there any one who also got this error and solve this issue?

Many thanks!

Ensure to use a proper image size before uploading. If the image is too big, you might receive error messages from the Image Manager tool. In addition, the permissions must be properly set on your FTP in order for the Image Manager tool to be able to successfully upload the images on your server. Refer to the install.txt file from your downloaded OC zip file from opencart.com to know which permission settings are required with OC.

That is most probably you have messed with javascript syntax by using either third party mods or u have changed in yr common.js or may be in header.twig file