message: [hotfix] dashboard fails when a slice is missing its datasource
diff: @@ -1620,7 +1620,7 @@ class Superset(BaseSupersetView):
  dash = qry.one()
  datasources = {slc.datasource for slc in dash.slices}
  for datasource in datasources:
  - if not self.datasource_access(datasource):
  + if datasource and not self.datasource_access(datasource):
  flash(
  __(get_datasource_access_error_msg(datasource.name)),
  "danger")
  