SyntaxError when installing extension

Hi

I am getting SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
Ok
<b>Warning</b>:ftp_chdir(): Can't change directory to public_html/: No such file or directory in <b>/home/anutracpanel/public_html/admin/controller/extension/installer.php</b> on line <b>299</b>
{"error":"Could not set root directory as ''}

Please help