Don't show help button if no support page is configured

[arbrandes]

Description

On a bare installation one sees the Help button even though no support page exists:

The result is a 404 if you click it.

Expected behavior

If no support page is configured, the Help button should simply not show.

Implementation

Since an MFE config variable already exists, we can simply check to see if it's populated before rendering.

[lkatsikaris]

I can take this issue @arbrandes