[repacker] fix fuzzer found memory leak.

Fixes https://oss-fuzz.com/testcase-detail/5196242811748352

src/graph/markbasepos-graph.hh

@@ -319,7 +319,8 @@ struct MarkBasePosFormat1 : public OT::Layout::GPOS_impl::MarkBasePosFormat1_2<S
     hb_vector_t<class_info_t> class_to_info;
 
     unsigned class_count= classCount;
-    class_to_info.resize (class_count);
+    if (!class_to_info.resize (class_count))
+      return hb_vector_t<class_info_t>();
 
     auto mark_array = c.graph.as_table<MarkArray> (this_index, &markArray);
     if (!mark_array) return hb_vector_t<class_info_t> ();
@@ -327,6 +328,7 @@ struct MarkBasePosFormat1 : public OT::Layout::GPOS_impl::MarkBasePosFormat1_2<S
     for (unsigned mark = 0; mark < mark_count; mark++)
     {
       unsigned klass = (*mark_array.table)[mark].get_class ();
+      if (klass >= class_count) continue;
       class_to_info[klass].marks.add (mark);
     }
 
@@ -335,6 +337,7 @@ struct MarkBasePosFormat1 : public OT::Layout::GPOS_impl::MarkBasePosFormat1_2<S
       unsigned mark = (link.position - 2) /
                      OT::Layout::GPOS_impl::MarkRecord::static_size;
       unsigned klass = (*mark_array.table)[mark].get_class ();
+      if (klass >= class_count) continue;
       class_to_info[klass].child_indices.push (link.objidx);
     }