Force remove sites-enabled directory, even when empty

contrib/dokku-installer.rb

@@ -16,7 +16,7 @@ if ARGV[0] == "onboot"
       f.puts "  }"
     f.puts "}"
   end
-  `rm /etc/nginx/sites-enabled/*`
+  `rm -f /etc/nginx/sites-enabled/*`
   puts "Installed Upstart service and default Nginx virtualhost for installer to run on boot."
   exit
 end

debian/preinst

@@ -18,7 +18,7 @@ case "$1" in
     echo '  }' >> $NGINX_CONF
     echo '}' >> $NGINX_CONF
 
-    rm /etc/nginx/sites-enabled/*
+    rm -f /etc/nginx/sites-enabled/*
     service nginx reload
     service dokku-installer start
     ;;