[Observium] "External Web URL" not set or incorrect,

I'm getting the message:

Setting 'web_url' for "External Web URL" not set or incorrect, please update on Global Settings Edit page.

I'm currently connecting to the URL:

https://observium.whoi.edu/

And the setting is:

http://observium.whoi.edu/

However, the settings page will not accept the 's' character. Every time I add it, it simply disappears again.

The defaults in includes/defaults.inc.php has:

#$config['base_url'] = "http://localhost/"; // Not recomend change this, only if autodetect wrong. Used in WUI #$config['web_url'] = "http://localhost:80/"; // This same as base_url but used only in cli for example in alerts

Should I change to:

$config['web_url'] = "https://localhost:443/"