[subset] minor cleanup.

src/hb-ot-layout-common.hh

@@ -1728,10 +1728,8 @@ struct Coverage
     // Cache the iterator result as it will be iterated multiple times
     // by the serialize code below.
     hb_sorted_vector_t<hb_codepoint_t> glyphs (it);
-
-    bool ret = bool (glyphs);
     Coverage_serialize (c->serializer, glyphs.iter ());
-    return_trace (ret);
+    return_trace (bool (glyphs));
   }
 
   bool sanitize (hb_sanitize_context_t *c) const