In libraries/Upload.php
Edit the function is_image().
add the ‘application/x-shockwave-flash’ in $img_mimes
$img_mimes = array(
'image/gif',
'image/jpeg',
'image/png',
'application/x-shockwave-flash',
);
It simply allow set_image_properties function to read the height & width for flash.
//now this will not call for flash
if ( ! $this->is_image())
{
return;
}