TagAlias.to_aliased: avoid query on blank arguments.

PostQueryBuilder calls `to_aliased` with empty arguments in some cases.
Return early to avoid a query in those cases.

app/models/tag_alias.rb

@@ -45,6 +45,7 @@ class TagAlias < TagRelationship
 
   def self.to_aliased(names)
     names = Array(names)
+    return names if names.empty?
     aliases = active.where(antecedent_name: names).map { |ta| [ta.antecedent_name, ta.consequent_name] }.to_h
     names.map { |name| aliases[name] || name }
   end