make data fixup resilient to missing submission rows

fixes CNVS-9349

test plan:
- no visible changes to submission version api
- the data fixup does not fail when version rows exist for non-existant
  submissions

Change-Id: I579808d94b1b32b1e87faaab1efb53f51ea82d7c
Reviewed-on: https://gerrit.instructure.com/26103
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>
Fixed style gauntlet regex to allow for negative values such as margin:-18px
Added spec for negative margin santize bug