fix conversation bug for observers w/ no observed users
fix conversation bug for observers w/ no observed users

Change-Id: I1287dfc681c8d727898c5f356d233d1f62a3cae9
Reviewed-on: https://gerrit.instructure.com/5370
Tested-by: Hudson <dfb64870173313a9a7b56f814c8e3b33e268497a@instructure.com>
Reviewed-by: Jacob Fugal <f862f167b85d41b225785c70d70808bc7337c1fe@instructure.com>

whalejasmine/canvas-lms,kyroskoh/canvas-lms,efrj/canvas-lms,AndranikMarkosyan/lms,sli7246/canvas_branch,wye0220/shindig-canvas,antoniuslin/canvas-lms,redconfetti/canvas-lms,Rvor/canvas-lms,ShreniiNepal/shrenii_lmp,em2/canvas-lms,tgroshon/canvas-lms,arrivu/hoodemo,SwinburneOnline/canvas-lms,wrdsb/canvas-lms,samuels410/greatlakes-lms,roxolan/canvas-lms,utkarshx/canvas-lms,rup/Tarrax,AndranikMarkosyan/lms,arrivu/hoodemo,tgroshon/canvas-lms,fronteerio/canvas-lms,samuels410/greatlakes-lms,eCNAP/CANVAS,sfu/canvas-lms,Rvor/canvas-lms,loganrun/pincan,sdeleon28/canvas-lms,landonwilkins/canvas-lms,venturehive/canvas-lms,gbleydon/canvas-lms,shidao-fm/canvas-lms,ankithbti/canvas_lms,dgynn/canvas-lms,ottenhoff/canvas-lms,wimemx/Canvas,arrivu/hiring-site,Jyaasa/canvas-lms,greyhwndz/canvas-lms,efrj/canvas-lms,skmezanul/canvas-lms,kyroskoh/canvas-lms,leftplusrightllc/canvas-lms,whalejasmine/canvas-lms,landonwilkins/canvas-lms,samuels410/greatlakes-lms,grahamb/canvas-lms,instructure/canvas-lms,whalejasmine/canvas-lms,Jyaasa/canvas-lms,Unow/ins,HotChalk/canvas-lms,wimemx/Canvas,eCNAP/CANVAS,juoni/canvas-lms,sdeleon28/canvas-lms,va7map/canvas-lms,roxolan/canvas-lms,Unow/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,wrdsb/canvas-lms,arrivu/arrivu-lms,em2/canvas-lms,wrdsb/canvas-lms,Jyaasa/canvas-lms,arrivu/qibla-ecampus,icelab/canvas,skmezanul/canvas-lms,snehakachroo1/LSI_replica,ottenhoff/canvas-lms,grahamb/canvas-lms,icelab/canvas,instructure/canvas-lms,jay3126/canvas-lms,efrj/canvas-lms,shidao-fm/canvas-lms,leftplusrightllc/canvas-lms,redconfetti/canvas-lms,Unow/ins,nditech/red-innovadores-lms,SwinburneOnline/canvas-lms,narigone/canvas,snehakachroo1/LSI_replica,faraazkhan/canvas,loganrun/pincan,narigone/canvas,arrivu/hiring-site,parbros/red-innovadores-lms,djbender/canvas-lms,roxolan/canvas-lms,rup/Tarrax,Rvor/canvas-lms,djbender/canvas-lms,leftplusrightllc/canvas-lms,dgynn/canvas-lms,AndranikMarkosyan/lms,nditech/red-innovadores-lms,leftplusrightllc/canvas-lms,icelab/canvas,tgroshon/canvas-lms,AndranikMarkosyan/lms,gbleydon/canvas-lms,HotChalk/canvas-lms,faraazkhan/canvas,merichar/canvas-lms,sfu/canvas-lms,kyroskoh/canvas-lms,juoni/canvas-lms,utkarshx/canvas-lms,landonwilkins/canvas-lms,antoniuslin/canvas-lms,loganrun/pincan,utkarshx/canvas-lms,venturehive/canvas-lms,jay3126/canvas-lms,sfu/canvas-lms,Jyaasa/canvas-lms,eCNAP/CANVAS,wye0220/shindig-canvas,greyhwndz/canvas-lms,sfu/canvas-lms,ShreniiNepal/shrenii_lmp,nditech/red-innovadores-lms,dgynn/canvas-lms,ankithbti/canvas_lms,ottenhoff/canvas-lms,wimemx/Canvas,em2/canvas-lms,merichar/canvas-lms,instructure/canvas-lms,HotChalk/canvas-lms,usmschuck/canvas,arrivu/hoodemo,shidao-fm/canvas-lms,arrivu/jigsaw-lms,va7map/canvas-lms,va7map/canvas-lms,jay3126/canvas-lms,usmschuck/canvas,arrivu/qibla-ecampus,Unow/canvas-lms,skmezanul/canvas-lms,sdeleon28/canvas-lms,kyroskoh/canvas-lms,arrivu/hiring-site,eCNAP/CANVAS,usmschuck/canvas,ankithbti/canvas_lms,arrivu/jigsaw-lms,ShreniiNepal/shrenii_lmp,instructure/canvas-lms,efrj/canvas-lms,grahamb/canvas-lms,antoniuslin/canvas-lms,HotChalk/canvas-lms,whalejasmine/canvas-lms,gbleydon/canvas-lms,nditech/red-innovadores-lms,arrivu/qibla-ecampus,venturehive/canvas-lms,narigone/canvas,matematikk-mooc/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,snehakachroo1/LSI_replica,Unow/ins,va7map/canvas-lms,arrivu/jigsaw-lms,sfu/canvas-lms,grahamb/canvas-lms,samuels410/greatlakes-lms,snehakachroo1/LSI_replica,instructure/canvas-lms,juoni/canvas-lms,jay3126/canvas-lms,grahamb/canvas-lms,djbender/canvas-lms,tgroshon/canvas-lms,dgynn/canvas-lms,matematikk-mooc/canvas-lms,roxolan/canvas-lms,wrdsb/canvas-lms,parbros/red-innovadores-lms,greyhwndz/canvas-lms,matematikk-mooc/canvas-lms,parbros/red-innovadores-lms,landonwilkins/canvas-lms,fronteerio/canvas-lms,utkarshx/canvas-lms,SwinburneOnline/canvas-lms,rup/Tarrax,usmschuck/canvas,sfu/canvas-lms,sdeleon28/canvas-lms,shidao-fm/canvas-lms,sfu/canvas-lms,fronteerio/canvas-lms,arrivu/arrivu-lms,Unow/canvas-lms,redconfetti/canvas-lms,fronteerio/canvas-lms,ShreniiNepal/shrenii_lmp,djbender/canvas-lms,skmezanul/canvas-lms,juoni/canvas-lms,instructure/canvas-lms,redconfetti/canvas-lms,greyhwndz/canvas-lms,antoniuslin/canvas-lms,sli7246/canvas_branch,narigone/canvas,faraazkhan/canvas,sli7246/canvas_branch,wye0220/shindig-canvas,Rvor/canvas-lms,merichar/canvas-lms,arrivu/arrivu-lms