main.analyze_stmt fails in bb-10.4-ps branch in --ps

build bb-10.4-ps branch, run ./mtr --ps main.analyze_stmt it'll fail on

analyze select * from t1 into @var;

because THD::prepare_explain_fields() does result->prepare(*field_list, NULL); and result is select_dumpvar expecting only one field in the result set, but field_list comes from make_explain_field_list().

please push the fix into bb-10.4-ps