bug#38248: help-follow-symbol silent when no symbol was found

[Eli Zaretskii]

> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Fri, 22 Nov 2019 20:40:15 +0100
> Cc: Lars Magne Ingebrigtsen <larsi@gnus.org>, 38248@debbugs.gnu.org
> 
> Currently, help-follow and help-follow-mouse signal an error if there's
> nothing to follow. However, help-follow-symbol does not, which means
> that C-c C-c in the help buffer when over an arbitrary non-symbol does
> nothing and says nothing.
> 
> That's not just inconsistent, but a bit disconcerting, as sometimes
> following a symbol can be slow. In my build, it takes a second or more
> to show the symbol documentation, so when there's no symbol I stand
> waiting for something to happen for a couple of seconds.

OK.