[subset] Retain all glyphs in preprocessed face.

src/hb-subset-input.cc

diff --git a/src/hb-subset-input.cc b/src/hb-subset-input.cc
index 232ab04..3217f72 100644
--- a/src/hb-subset-input.cc
+++ b/src/hb-subset-input.cc
@@ -468,6 +468,9 @@
   hb_set_clear (hb_subset_input_set(input, HB_SUBSET_SETS_UNICODE));
   hb_set_invert (hb_subset_input_set(input, HB_SUBSET_SETS_UNICODE));
 
+  hb_set_clear (hb_subset_input_set(input, HB_SUBSET_SETS_GLYPH_INDEX));
+  hb_set_invert (hb_subset_input_set(input, HB_SUBSET_SETS_GLYPH_INDEX));
+
   hb_set_clear (hb_subset_input_set(input,
                                     HB_SUBSET_SETS_LAYOUT_FEATURE_TAG));
   hb_set_invert (hb_subset_input_set(input,