Replace a couple of malloc()s with calloc()

src/hb-shape-plan.cc

diff --git a/src/hb-shape-plan.cc b/src/hb-shape-plan.cc
index 1d94c52..56e2ea5 100644
--- a/src/hb-shape-plan.cc
+++ b/src/hb-shape-plan.cc
@@ -128,7 +128,7 @@
     face = hb_face_get_empty ();
   if (unlikely (!props))
     return hb_shape_plan_get_empty ();
-  if (num_user_features && !(features = (hb_feature_t *) malloc (num_user_features * sizeof (hb_feature_t))))
+  if (num_user_features && !(features = (hb_feature_t *) calloc (num_user_features, sizeof (hb_feature_t))))
     return hb_shape_plan_get_empty ();
   if (!(shape_plan = hb_object_create<hb_shape_plan_t> ())) {
     free (features);