message: Keep same error code with PHP when file is empty.
diff: @@ -793,7 +793,7 @@ static int multipart_body_on_header_value(multipart_parser* p, const char *at, s
  sw_add_assoc_string(multipart_header, "name", "", 1);
  sw_add_assoc_string(multipart_header, "type", "", 1);
  sw_add_assoc_string(multipart_header, "tmp_name", "", 1);
  - add_assoc_long(multipart_header, "error", HTTP_UPLOAD_ERR_PARTIAL);
  + add_assoc_long(multipart_header, "error", HTTP_UPLOAD_ERR_NO_FILE);
  add_assoc_long(multipart_header, "size", 0);
  strncpy(value_buf, Z_STRVAL_P(filename), Z_STRLEN_P(filename));
  @@ -955,8 +955,11 @@ static int multipart_body_on_data_end(multipart_parser* p)
  if (p->fp != NULL)
  {
  long size = swoole_file_get_size((FILE*) p->fp);
  + if (size > 0)
  + {
  add_assoc_long(multipart_header, "error", HTTP_UPLOAD_ERR_OK);
  add_assoc_long(multipart_header, "size", size);
  + }
  fclose((FILE *) p->fp);
  p->fp = NULL;
  