Update rasa/core/tracker_store.py
Update rasa/core/tracker_store.py

Co-authored-by: ricwo <6d01c4d5f3745701436bc9aec9854ad11680340d@users.noreply.github.com>
RasaHQ/rasa_nlu,RasaHQ/rasa_nlu,RasaHQ/rasa_nlu