Filter empty array from Convsersation sql
Filter empty array from Convsersation sql

refs VICE-2406
flag=none

When conversation_ids returns empty
it breaks the sql. This filters those returns
so it doesnt break the site.

Test Plan:
We will run this on beta, to see if it stops
the 500 from being generated.

Change-Id: Ie35623eed6d88b275812d532ec30b6edff3dceba
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/284086
Reviewed-by: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>
Reviewed-by: Omar Soto-Fortuño <2ca100155bc0669318a7e6f3850629c7667465e1@instructure.com>
QA-Review: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Product-Review: Omar Soto-Fortuño <2ca100155bc0669318a7e6f3850629c7667465e1@instructure.com>

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