[subset-plan] Another error check

src/hb-subset-accelerator.hh

@@ -58,6 +58,8 @@ struct hb_subset_accelerator_t
     hb_subset_accelerator_t* accel =
         (hb_subset_accelerator_t*) hb_calloc (1, sizeof(hb_subset_accelerator_t));
 
+    if (unlikely (!accel)) return accel;
+
     new (accel) hb_subset_accelerator_t (unicode_to_gid_,
 					 gid_to_unicodes_,
 					 unicodes_,

src/hb-subset-plan.cc

@@ -1052,6 +1052,8 @@ hb_subset_plan_t::hb_subset_plan_t (hb_face_t *face,
 				       gid_to_unicodes,
                                        unicodes,
 				       has_seac);
+
+    check_success (inprogress_accelerator);
   }
 
 #define HB_SUBSET_PLAN_MEMBER(Type, Name) check_success (!Name.in_error ());