Copy the fix for "WP_Admin_Bar::add_node was called incorrectly" into 0.5-dev

[benlk]

Changes

This closes #1349 in the 0.5 branch. It fixes a spacing error.

Why

Because seeing this in the console log for every single page load makes debugging annoying:

2018/07/31 11:18:49 [error] 33695#0: *39 FastCGI sent in stderr: "PHP message: PHP Notice: WP_Admin_Bar::add_node was called incorrectly. The menu ID should not be empty. Please see Debugging in WordPress for more information. (This message was added in version 3.3.0.) in /Users/blk/sites/largo/wp-includes/functions.php on line 4161" while reading upstream, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/Users/blk/.valet/valet.sock:", host: "largo.test"

And because RC's commit 6e8587a wasn't in the present Largo.