clipboard: set fd member of clipboard_source

The fd member of clipboard_source structure was not set
but was used in close().

v2. don't do unnecessary changes

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/clipboard.c

@@ -151,6 +151,7 @@ clipboard_source_create(struct clipboard *clipboard,
 	source->refcount = 1;
 	source->clipboard = clipboard;
 	source->serial = serial;
+	source->fd = fd;
 
 	s = wl_array_add(&source->base.mime_types, sizeof *s);
 	if (s == NULL)