Fix bfi_thumb.php for Pantheon directories

bfi_thumb.php

<?php

// Create the upload subdirectory, this is where
// we store all our generated images
if ( defined( 'BFITHUMB_UPLOAD_DIR' ) ) {
    $upload_dir .= "/" . BFITHUMB_UPLOAD_DIR;
    $upload_url .= "/" . BFITHUMB_UPLOAD_DIR;
} else {
    $upload_dir .= "/bfi_thumb";
    $upload_url .= "/bfi_thumb";
}

// Patch upload directory value for creating new directories based on manipulations.
$param_hash = md5(implode('', array_values(ksort($params) ? $params : $params)));
$upload_dir .= "/{$param_hash}";
$upload_url .= "/{$param_hash}";

if ( ! is_dir( $upload_dir ) ) {
    wp_mkdir_p( $upload_dir );
}