After upgrading to 0.99f version, you get this error on any dashboard:
Starting from Grafana 4.5, the version of the graphite datasource is mandatory and that’s why we update a record in the sqlite database during the upgrade process. For a small population of users, this record is not updated for an unknown reason.
To correct that issue, you simply need to force the “0.9” version in the graphite datasource: