bindings: cxx: add a missing throw to line::event_get_fd()
bindings: cxx: add a missing throw to line::event_get_fd()

If the call to gpiod_line_event_get_fd() fails, we're not actually
throwing the exception - we're only creating it on stack. Add the
missing throw keyword.

Fixes: 8078a4a2ad90 ("bindings: implement C++ bindings")
Signed-off-by: Bartosz Golaszewski <e5d45fddd9040473413b909b802f629a971ad04c@baylibre.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod