DEV-39995: the help browser would crash on open if the media ctrl returned no media plugin for text/html (NULL dereference), which seems to be happening in viewer-2.0.0-3 for me at the moment.
DEV-39995: the help browser would crash on open if the media ctrl
returned no media plugin for text/html (NULL dereference), which seems
to be happening in viewer-2.0.0-3 for me at the moment.

Clearly there's not too much to do if we can't display HTML, but this
fix will at least stop the help browser from crashing.

gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm