bug#24041: 25.1.50; xwidget + -nw mode gives segfault

[Robert Cochran]

First, apologies for having left this alone this long. I meant to get to
it earlier.

Anyways, so the fix here is conceptually pretty simple: have a check in
place to ensure (display-graphic-p) returns non-nil before doing any
xwidgets stuff. Easy enough.

What I want to solicit feedback on before I write a patch is this: who
should be responsible for this check? Should the function provider (the
xwidget C 'library') check for the proper support? Or should that be
left to the user (the Lisp that calls the xwidget functions, in this
case `xwidget-webkit-browse-url`)?

Personal opinion is that xwidget should check: that way a Lisp caller
can't forget to do so. But I'm largely unaware of the conventions on how
to handle this, so I want to make sure I'm doing the correct thing
before I make a style mistake.

Thanks,
-- 
~Robert Cochran

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