Sync Data Mongo

I have that error in logstash logs when logstash starting. Here my config file for logstash:
input {
mongodb {
uri => 'mongodb://shardsvr1:27017,shardsvr2:27017,shardsvr3:27017/db_mongo?replicaSet=RplS'
placeholder_db_dir => '/opt/logstash-mongodb/'
placeholder_db_name => 'logstash_sqlite_backup_.db'
collection => "log_history_control_\d{4}-\d{2}$"
batch_size => 10000

Please do not post pictures of text. They are not searchable and some folks cannot read them.

The code is blowing up here. I think the find is returning nil, which probably means the collection is empty.