message: Fix error message in expression parser
diff: @@ -22,7 +22,7 @@ parser_result<Code> parse_expr(const uint8_t* pos)
  switch (instr)
  {
  default:
  - throw parser_error{"invalid instruction " + std::to_string(*pos)};
  + throw parser_error{"invalid instruction " + std::to_string(*(pos - 1))};
  case Instr::unreachable:
  case Instr::nop:
  