DEV: Instance#replace_flags block should be optional

DEV: Instance#replace_flags block should be optional

diff --git a/lib/plugin/instance.rb b/lib/plugin/instance.rb
index 711dd56..01ac030 100644
--- a/lib/plugin/instance.rb
+++ b/lib/plugin/instance.rb
@@ -151,7 +151,7 @@ class Plugin::Instance
   def replace_flags(settings: ::FlagSettings.new, score_type_names: [])
     next_flag_id = ReviewableScore.types.values.max + 1
 
-    yield(settings, next_flag_id)
+    yield(settings, next_flag_id) if block_given?
 
     reloadable_patch do |plugin|
       ::PostActionType.replace_flag_settings(settings)

GitHub sha: 6b4cebed