Bug#40972: Partition pruning can lead to crash for bad dates

post push fix, added test found a valgrind warning

sql/sql_partition.cc:
  Bug#40972: Partition pruning can lead to crash for bad dates
  
  Fix for valgrind warning

sql/sql_partition.cc

@@ -6678,6 +6678,7 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
   uint32             max_endpoint_val;
   get_endpoint_func  get_endpoint;
   uint field_len= field->pack_length_in_rec();
+  part_iter->ret_null_part= part_iter->ret_null_part_orig= FALSE;
 
   if (part_info->part_type == RANGE_PARTITION)
   {
@@ -6698,7 +6699,6 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
     max_endpoint_val=    part_info->no_list_values;
     part_iter->get_next= get_next_partition_id_list;
     part_iter->part_info= part_info;
-    part_iter->ret_null_part= part_iter->ret_null_part_orig= FALSE;
     if (max_endpoint_val == 0)
     {
       /*