This is happening in basically every application, due to implementation
changes in GtkStyleContext

https://bugzilla.gnome.org/show_bug.cgi?id=761577

The current default URI when none is explicitly specified is "help:gnome-help",
which maps to the GNOME 3 desktop users guide. If this is not specified, yelp
now will fallback to showing 'help-list:', which is always available.

The new fallback applies both when launched through command line or when a new
yelp window is requested.

The patch also avoids a YelpUri memleak that was happening in
yelp_application_new_window(), as yelp_application_new_window_uri() was itself
taking its own reference.

https://bugzilla.gnome.org/show_bug.cgi?id=759545

It's a GSourceFunc, so it'd better return a gboolean. This doesn't seem
to be causing any problems in Fedora, but in Endless it's causing 100%
CPU usage after executing a search, because the source never gets
removed.

https://bugzilla.gnome.org/show_bug.cgi?id=761647

https://bugzilla.gnome.org/show_bug.cgi?id=757139

Since we switched to use custom URI schemes we no longer support loading
file URIs. We need to detect the document pointed by the given URI and
build an appropriate URI (ghelp, man, info, ...).

https://bugzilla.gnome.org/show_bug.cgi?id=753443

https://bugzilla.gnome.org/show_bug.cgi?id=756654