[subset] reset the visited lookup count before each closure iteration.

src/hb-ot-layout-gsubgpos.hh

@@ -81,6 +81,9 @@ struct hb_closure_context_t :
     nesting_level_left++;
   }
 
+  void reset_lookup_visit_count ()
+  { lookup_count = 0; }
+
   bool lookup_limit_exceeded ()
   { return lookup_count > HB_MAX_LOOKUP_VISIT_COUNT; }
 

src/hb-ot-layout.cc

@@ -1530,6 +1530,7 @@ hb_ot_layout_lookups_substitute_closure (hb_face_t      *face,
   unsigned int glyphs_length;
   do
   {
+    c.reset_lookup_visit_count ();
     glyphs_length = glyphs->get_population ();
     if (lookups)
     {