Cannot use a scalar value as an array

I'm getting a bunch of PHP errors every time when i upload an image
Warning: Cannot use a scalar value as an array in block_page_build() (line 269 of /home/account/public_html/drupal/modules/block/block.module).

After i investigating the problem, i resolved it remove the "return TRUE;" line from plup_upload_page function.

function plup_upload_page(){
{
....

drupal_json_output($return);
}

//return TRUE;
}