Move by_domain/local interaction check to filter (#39216)

app/models/custom_emoji_filter.rb

@@ -19,7 +19,7 @@ class CustomEmojiFilter
   def results
     scope = CustomEmoji.alphabetic
 
-    params.each do |key, value|
+    relevant_params.each do |key, value|
       next if IGNORED_PARAMS.include?(key.to_s)
 
       scope.merge!(scope_for(key, value)) if value.present?
@@ -30,6 +30,12 @@ class CustomEmojiFilter
 
   private
 
+  def relevant_params
+    params.tap do |args|
+      args.delete(:by_domain) if args[:local].present?
+    end
+  end
+
   def scope_for(key, value)
     case key.to_s
     when 'local'