In logstash there is no way to filter out an empty string.
If the stack_trace is an empty string, it should have a null value.
This will make it much easier to filter out user browser extensions that have no stack trace.
Examples of errors I'd like to filter out:
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2020.10.22/clienterror/?id=AXVR9aq9LNRtRo5X_GQV
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2020.10.21/clienterror/?id=AXVL49Up2lgCwKx7sOBL