don't try to get plugin name if no migration_type is set
don't try to get plugin name if no migration_type is set

refs #4429

Change-Id: I647861957a2bc6454f8e1bbd28b210957ab1e21e
Reviewed-on: https://gerrit.instructure.com/3424
Reviewed-by: Zach Wily <9de8c4480303b5335cd2a33eefe814615ba3612a@instructure.com>
Tested-by: Hudson <dfb64870173313a9a7b56f814c8e3b33e268497a@instructure.com>

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