Just had the same issue, i think PR #151 that I just published should fix it (plus bumping chart versions of course)

as a workaround until this fix is released, you can use the following workaround:

      volumes:
      - name: config
        path: /config/config.yml
        subPath: config.yml
        existingSecret: secret
        existingClaim: dummy

by using existingClaim to a dummy value, the pvc won't be created, and it won't be used at all because existingSecret is used for the mount as it has precedence in the template.

note: only tested that this works on the cron job chart, dont know if it works on the regular one.