Error when using user="username"

Hello,

Could you please assist me with this issue? When I use the following shortcode:
[xprofile field=179 user=”DJohnson”]

I get this error:
Catchable fatal error: Object of class WP_User could not be converted to string in /…/wp-content/plugins/buddypress/bp-xprofile/classes/class-bp-xprofile-profiledata.php on line 369

This is the code for that section for line 369

// Assemble uncached IDs
		$uncached_ids = array();
		foreach ( $user_ids as $user_id ) {
			$cache_key = "{$user_id}:{$field_id}";
			if ( false === wp_cache_get( $cache_key, 'bp_xprofile_data' ) ) {
				$uncached_ids[] = $user_id;
			}
		}

Thanks in advance!

https://ww.wp.xz.cn/plugins/bp-xprofile-shortcode/