Fix hunspell::NodeReader::affix_id_for_leaf() bounds check

This method checks for 3 bytes of available data, but reads only 2 bytes.

Change-Id: I504e9ed6cda18907a3f74cd931ef97d910043df5
Reviewed-on: https://chromium-review.googlesource.com/1185019Reviewed-by: Rachel Blum <groby@chromium.org>
Commit-Queue: Rachel Blum <groby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585076}

third_party/hunspell/google/bdict_reader.cc

@@ -76,7 +76,7 @@ class NodeReader {
   // additional affix IDs following the node when leaf_has_following is set,
   // but this will not handle those.
   inline int affix_id_for_leaf() const {
-    if (node_offset_ >= bdict_length_ - 2) {
+    if (node_offset_ >= bdict_length_ - 1) {
       is_valid_ = false;
       return 0;
     }