btr_next_buffer_omit(): Add comment on passing NULL pointer.

It has always been OK to pass a NULL buffer pointer to this function,
but this was not documented yet.

diff --git a/buffer_tree.c b/buffer_tree.c
index 5756898bced710406b3c68b8cb1e5cc85a992183..30f875fa7b3526794f41be11c4f4e9e8353ccb11 100644 (file)
--- a/buffer_tree.c
+++ b/buffer_tree.c
@@ -602,7 +602,7 @@ static size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char
  *
  * \param btrn The node whose input queue is to be queried.
  * \param omit Number of bytes to be omitted.
- * \param bufp Result pointer.
+ * \param bufp Result pointer. It is OK to pass \p NULL here.
  *
  * If a buffer tree node needs more input data but can not consume the data it
  * already has (because it might be needed again later) this function can be