Fix #83 - if user cannot be found (or is self) throw error, don't return empty 200

This prevents the undefined profile from being opened in the first place on such an error

app/services/follow_service.rb

@@ -5,7 +5,7 @@ class FollowService < BaseService
   def call(source_account, uri)
     target_account = follow_remote_account_service.call(uri)
 
-    return nil if target_account.nil? || target_account.id == source_account.id
+    raise ActiveRecord::RecordNotFound if target_account.nil? || target_account.id == source_account.id
 
     follow = source_account.follow!(target_account)