[SingleSubstFormat1] Help avoid timeouts in closure() some more

For https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49712

src/OT/Layout/GSUB/SingleSubstFormat1.hh

@@ -42,6 +42,11 @@ struct SingleSubstFormat1_3
     hb_codepoint_t d = deltaGlyphID;
     hb_codepoint_t mask = get_mask ();
 
+    /* Help fuzzer avoid this function as much. */
+    unsigned pop = (this+coverage).get_population ();
+    if (pop >= mask)
+      return;
+
     hb_set_t intersection;
     (this+coverage).intersect_set (c->parent_active_glyphs (), intersection);
 
@@ -52,7 +57,7 @@ struct SingleSubstFormat1_3
     hb_codepoint_t max_before = intersection.get_max ();
     hb_codepoint_t min_after = (min_before + d) & mask;
     hb_codepoint_t max_after = (max_before + d) & mask;
-    if ((this+coverage).get_population () >= max_before - min_before &&
+    if (pop >= max_before - min_before &&
 	((min_before <= min_after && min_after <= max_before) ||
 	 (min_before <= max_after && max_after <= max_before)))
       return;