value of mandatory string field isn't saved

[v-instrumentix]

Data feed starts with "Hello" message, then multiple "Data" messages follow. All messages have the same header. Template looks as follows:

...
  <template name="T_HEAD" dictionary="template">
    <string name="Field"><copy/></string>
    ...
  </template>

  <template name="Hello" dictionary="template" id="54321">
    <string name="MsgType"><constant value="Ehlo"/></string>
    <group name="Head" presence="optional">
      <templateRef name="T_HEAD"/>
    </group>
    ...
  </template>

  <template name="Data" dictionary="template" id="54322">
    <string name="MsgType"><constant value="Data"/></string>
    <group name="Head" presence="optional">
      <templateRef name="T_HEAD"/>
    </group>
    ...
  </template>
...

On decode side initial "Hello" is processed with no problems, but decode of first "Data" fails:

/home/v/src/mfast-HEAD/src/mfast/coder/decoder/decoder_field_operator.cpp(232): Throw in function void mfast::decoder_detail::copy_or_increment_operator_impl<Operation>::decode_impl(const T&, mfast::fast_istream&, mfast::decoder_presence_map&) const [with T = mfast::string_mref; Operation = mfast::decoder_detail::null_operation] Dynamic exception type: boost::exception_detail::clone_implmfast::fast_dynamic_error std::exception::what: std::exception [mfast::tag_error_code*] = D5

[v-instrumentix]

UPD: please ignore last comment (stroke though).