An empty database prefix is not supported for multisite. <small>Add a sanity check anyway.</small> see #19566.

git-svn-id: http://core.svn.wordpress.org/trunk@19641 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: nacin

wp-includes/user.php

@@ -696,7 +696,7 @@ function get_blogs_of_user( $user_id, $all = false ) {
 	foreach ( $keys as $key ) {
 		if ( 'capabilities' !== substr( $key, -12 ) )
 			continue;
-		if ( 0 !== strpos( $key, $wpdb->base_prefix ) )
+		if ( $wpdb->base_prefix && 0 !== strpos( $key, $wpdb->base_prefix ) )
 			continue;
 		$blog_id = str_replace( array( $wpdb->base_prefix, '_capabilities' ), '', $key );
 		if ( ! is_numeric( $blog_id ) )