fix /dashboard/data_exports page error when not logged in
fix /dashboard/data_exports page error when not logged in

test plan:
 - /dashboard/data_exports should take you to the
   "Download Submissions" page if you're logged in
 - and it should take you to the login page, not a page
   error, if you're not

fixes CANVAS-HYDE

Change-Id: I5e941e4c83745395e0c5e6309f54dc7afe256159
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/293328
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Aaron Ogata <11ccf682c06d1508642f943a3962a1c3d00b8e44@instructure.com>
QA-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
Product-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms