Do not raise an error if PrecomputeFeed could not find any status (#4015)

app/services/precompute_feed_service.rb

@@ -16,7 +16,7 @@ class PrecomputeFeedService < BaseService
     pairs = statuses.reverse_each.map(&method(:process_status))
 
     redis.pipelined do
-      redis.zadd(account_home_key, pairs)
+      redis.zadd(account_home_key, pairs) if pairs.any?
       redis.del("account:#{@account.id}:regeneration")
     end
   end

spec/services/precompute_feed_service_spec.rb

@@ -18,5 +18,10 @@ RSpec.describe PrecomputeFeedService do
 
       expect(Redis.current.zscore(FeedManager.instance.key(:home, account.id), reblog.id)).to eq status.id
     end
+
+    it 'does not raise an error even if it could not find any status' do
+      account = Fabricate(:account)
+      subject.call(account)
+    end
   end
 end