Fix #3639: Favorite count pixiv tags aren't skipped by translated tags.

app/logical/sources/strategies/base.rb

@@ -83,6 +83,8 @@ module Sources
 
       # Given a tag from the source site, should return an array of corresponding Danbooru tags.
       def translate_tag(untranslated_tag)
+        return [] if untranslated_tag.blank?
+
         translated_tag_names = WikiPage.active.other_names_equal(untranslated_tag).uniq.pluck(:title)
         translated_tag_names = TagAlias.to_aliased(translated_tag_names)
         translated_tags = Tag.where(name: translated_tag_names)

app/logical/sources/strategies/pixiv.rb

@@ -57,7 +57,7 @@ module Sources
       end
 
       def translate_tag(tag)
-        normalized_tag = tag.gsub(/\A(\S+?)_?\d+users入り\Z/i, '\1')
+        normalized_tag = tag.gsub(/\d+users入り\z/i, "")
 
         translated_tags = super(normalized_tag)
         if translated_tags.empty? && normalized_tag.include?("/")