Subdirectory URL without trailing slash causes 403 error about october HOT 4 CLOSED

<IfModule mod_rewrite.c>
    <IfModule mod_negotiation.c>
        Options -MultiViews
    </IfModule>

    RewriteEngine On

    ##
    ## Directory Listing attempts
    ##
    DirectorySlash Off
    RewriteOptions AllowNoSlash

    ##
    ## Redirect trailing slashes
    ##
    RewriteRule ^(.*)/$ /$1 [L,R=301]

    ##
    ## Handle resource requests
    ##
    RewriteCond %{REQUEST_URI} combine/.*(.css|.js)
    RewriteRule ^ index.php [L]

    ##
    ## White listed folders and files
    ##
    RewriteCond %{REQUEST_FILENAME} -f
    RewriteCond %{REQUEST_URI} !\.js
    RewriteCond %{REQUEST_URI} !\.ico
    RewriteCond %{REQUEST_URI} !\.jpg
    RewriteCond %{REQUEST_URI} !\.gif
    RewriteCond %{REQUEST_URI} !\.css
    RewriteCond %{REQUEST_URI} !\.less
    RewriteCond %{REQUEST_URI} !\.scss
    RewriteCond %{REQUEST_URI} !\.png
    RewriteCond %{REQUEST_URI} !\.swf
    RewriteCond %{REQUEST_URI} !\.txt
    RewriteCond %{REQUEST_URI} !\.xml
    RewriteCond %{REQUEST_URI} !\.xls
    RewriteCond %{REQUEST_URI} !\.eot
    RewriteCond %{REQUEST_URI} !\.woff
    RewriteCond %{REQUEST_URI} !\.ttf
    RewriteCond %{REQUEST_URI} !\.svg
    RewriteCond %{REQUEST_URI} !docs/.*
    RewriteCond %{REQUEST_URI} !themes/.*
    RewriteRule ^ index.php [L]

    ##
    ## Standard routes
    ##
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ index.php [L]

</IfModule>