WSGI dashboard plugin with unknown icon crashes GUI

[YngveNPettersen]

In our buildbot configuration we have some WSGI dashboard plugins.

When I started migrating these to React with the update to 3.11, the whole GUI crashed and became blank, with several messages in the console linking the React Error 130.

I eventually tracked the problem down to the icons specified in the plugins. If the icon named in the config dictionary does not exist, e.g. "fa-browser" (which works in Buildbot 3.7), the GUI crashes.