As per the Wayland spec [1]:
> The icon surface is an optional (can be NULL) surface that provides an
> icon to be moved around with the cursor.
However, as of now Sway "start_drag" signal handler does not starts the
DND session unless a non-NULL drag icons is provided. This patch fixes
it by skipping handling of the drag icon if it is null.
Fixes#5509
[1] https://wayland.freedesktop.org/docs/html/apa.html#protocol-spec-wl_data_device
Signed-off-by: Nick Diego Yamane <nickdiego@igalia.com>
e5954f321f