[subset] Use glyphset gsub for layout variation indices collection.
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index b58c27e..d055783 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -256,7 +256,11 @@
 
 #ifndef HB_NO_VAR
   if (close_over_gdef)
-    _collect_layout_variation_indices (plan->source, plan->_glyphset, plan->gpos_lookups, plan->layout_variation_indices, plan->layout_variation_idx_map);
+    _collect_layout_variation_indices (plan->source,
+                                       plan->_glyphset_gsub,
+                                       plan->gpos_lookups,
+                                       plan->layout_variation_indices,
+                                       plan->layout_variation_idx_map);
 #endif
 
 #ifndef HB_NO_SUBSET_CFF