title: blastn -mt_mode 1 -num_threads 24 terminate called after throwing an instance of 'std::length_error'
body: <p>When I was running blastn v2.12.0 with multithreaded mode (-num_thread 24), split by query(-mt_mode 1), I have the following error:</p>
  <p>terminate called after throwing an instance of 'std::length_error'
  what():  basic_string::_M_create</p>
  <p>for a supercomputer (RHEL 7/cent OS), this happened but for a self-owned ubuntu v18.0.4, this did not happen.</p>
  <p>Blast team do not respond so I posted it here.</p>
  <p>Many Thanks</p>