message: fix: properly mark slot rendered flag in production mode
  fix
diff: @@ -27,12 +27,14 @@ export function renderSlot (
  } else {
  const slotNodes = this.$slots[name]
  // warn duplicate slot usage
  - if (slotNodes && process.env.NODE_ENV !== 'production') {
  - slotNodes._rendered && warn(
  + if (slotNodes) {
  + if (process.env.NODE_ENV !== 'production' && slotNodes._rendered) {
  + warn(
  `Duplicate presence of slot "${name}" found in the same render tree ` +
  `- this will likely cause render errors.`,
  this
  )
  + }
  slotNodes._rendered = true
  }
  return slotNodes || fallback
  