[set] Use references, not pointers, in internal C++ API
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index 56d66e1..62137bf 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -285,7 +285,7 @@
   hb_set_t glyphset_colrv0;
   if (colr.is_valid ())
   {
-    glyphset_colrv0.union_ (cur_glyphset);
+    glyphset_colrv0.union_ (*cur_glyphset);
     for (hb_codepoint_t gid : cur_glyphset->iter ())
       colr.closure_glyphs (gid, &glyphset_colrv0);
     cur_glyphset = &glyphset_colrv0;