Save to subdirectory based on post_date, and fix for Windows

[scottpoulin]

To save images based on post_date to subfolder /uploads/year/month rather than current year/month, in file imageUploader.php, function getUploadDir, line 105, was:

if ($this->_uploadDir === null) {
    $this->_uploadDir = wp_upload_dir(date('Y/m', strtotime( $this->post['post_date'] ) ));
}

change to:

if ($this->_uploadDir === null) {
    if ( isset( $this->post['post_date'] ) ) {
        $this->_uploadDir = wp_upload_dir(date('Y/m', strtotime( $this->post['post_date'] ) ));
    } else {
        $this->_uploadDir = wp_upload_dir(date('Y/m', time()));
    }
}

In Windows (at least running WAMP), WP constant DIRECTORY_SEPARATOR is set to '', which is removed when written to the database, resulting in broken URLs like /wp-content/uploads/2023/05imagefilename.jpg instead of /wp-content/uploads/2023/05/imagefilename.jpg. I don't know if this will be the case for all Windows installs, but if you run into issues, just search/replace DIRECTORY_SEPARATOR with '/' in file imageUploader.php.