bcachefs: darray: Don't pass NULL to memcpy()

memcpy's second parameter must not be NULL, even if size is zero.
Signed-off-by: Tavian Barnes <tavianator@tavianator.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/darray.c

@@ -13,7 +13,8 @@ int __bch2_darray_resize(darray_char *d, size_t element_size, size_t new_size, g
 		if (!data)
 			return -ENOMEM;
 
-		memcpy(data, d->data, d->size * element_size);
+		if (d->size)
+			memcpy(data, d->data, d->size * element_size);
 		if (d->data != d->preallocated)
 			kvfree(d->data);
 		d->data	= data;