bug#33294: xwidget-insert crashes Emacs

[Eli Zaretskii <eliz@gnu.org>]

> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Wed, 07 Nov 2018 16:16:00 +0000
> 
> Unrelated to this bug, but a quick look at the code shows that
> xwidget-insert calls make-xwidget, which returns an uninitialized object
> if the type argument is not 'webkit.

Not sure I follow: this part of the code seems to initialize the
object that is returned even if TYPE is not 'webkit':

  struct xwidget *xw = allocate_xwidget ();
  Lisp_Object val;
  xw->type = type;
  xw->title = title;
  xw->buffer = NILP (buffer) ? Fcurrent_buffer () : Fget_buffer_create (buffer);
  xw->height = XFASTINT (height);
  xw->width = XFASTINT (width);
  xw->kill_without_query = false;
  XSETXWIDGET (val, xw);
  Vxwidget_list = Fcons (val, Vxwidget_list);
  xw->widgetwindow_osr = NULL;
  xw->widget_osr = NULL;
  xw->plist = Qnil;