Missing slash in RewriteCond using $drupal_subdir

In boost_admin_generate_htaccess() the variable $drupal_subdir is used in the line:

$string .= " RewriteCond %{REQUEST_URI} (^$drupal_subdir(admin|$cache_dir|misc|modules|sites|system|openid|themes|node/add))|(/(comment/reply|edit
|user|user/(login|password|register))$) [OR]\n";

At the start of this function a trailing slash is removed from $drupal_subdir, therefore this way it would match e.g. drupaladmin and drupalmisc

With the attached patch it generates a working RewtiteCond like
(^/drupal/(admin|cache|misc|modules|sites|system|openid|themes|node/add))

Changing all uses of $drupal_subdir to include a trailing slash might be a slightly cleaner implementation though...