message: Set undefined highlight tags
diff: @@ -5,6 +5,8 @@ function replaceHighlightTags(value, highlightPreTag, highlightPostTag) {
  // If the value of the attribute is a string,
  // the highlight is applied by MeiliSearch (<em> tags)
  // and we replace the <em> by the expected tag for InstantSearch
  + highlightPreTag = highlightPreTag || '__ais-highlight__'
  + highlightPostTag = highlightPostTag || '__/ais-highlight__'
  if (isString(value)) {
  newHighlightValue = value
  .replace(/<em>/g, highlightPreTag)
  