fix file chooser in add-module-item dialog
fix file chooser in add-module-item dialog

test plan: when adding a file to a module itme, the "Choose File"
button should not appear until "[ New File ]" is selected

fixes CNVS-19748

Change-Id: I4dea0e5c6f79dd81c090c58b810cfe9b032b2091
Reviewed-on: https://gerrit.instructure.com/52479
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
QA-Review: Jahnavi Yetukuri <ed2b2672ccc2e59e56c0615df7f01b579202e014@instructure.com>
Tested-by: Jenkins
Product-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>

shidao-fm/canvas-lms,fronteerio/canvas-lms,va7map/canvas-lms,efrj/canvas-lms,SwinburneOnline/canvas-lms,ShreniiNepal/shrenii_lmp,whalejasmine/canvas-lms,matematikk-mooc/canvas-lms,jay3126/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,antoniuslin/canvas-lms,redconfetti/canvas-lms,matematikk-mooc/canvas-lms,djbender/canvas-lms,narigone/canvas,eCNAP/CANVAS,tgroshon/canvas-lms,dgynn/canvas-lms,AndranikMarkosyan/lms,Rvor/canvas-lms,wrdsb/canvas-lms,snehakachroo1/LSI_replica,redconfetti/canvas-lms,shidao-fm/canvas-lms,Jyaasa/canvas-lms,greyhwndz/canvas-lms,AndranikMarkosyan/lms,tgroshon/canvas-lms,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,sfu/canvas-lms,redconfetti/canvas-lms,Jyaasa/canvas-lms,jay3126/canvas-lms,sdeleon28/canvas-lms,efrj/canvas-lms,venturehive/canvas-lms,fronteerio/canvas-lms,kyroskoh/canvas-lms,snehakachroo1/LSI_replica,HotChalk/canvas-lms,leftplusrightllc/canvas-lms,Rvor/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,juoni/canvas-lms,grahamb/canvas-lms,antoniuslin/canvas-lms,efrj/canvas-lms,roxolan/canvas-lms,SwinburneOnline/canvas-lms,leftplusrightllc/canvas-lms,skmezanul/canvas-lms,wrdsb/canvas-lms,instructure/canvas-lms,juoni/canvas-lms,juoni/canvas-lms,utkarshx/canvas-lms,djbender/canvas-lms,skmezanul/canvas-lms,sdeleon28/canvas-lms,matematikk-mooc/canvas-lms,Jyaasa/canvas-lms,AndranikMarkosyan/lms,greyhwndz/canvas-lms,grahamb/canvas-lms,dgynn/canvas-lms,venturehive/canvas-lms,roxolan/canvas-lms,juoni/canvas-lms,instructure/canvas-lms,tgroshon/canvas-lms,va7map/canvas-lms,sfu/canvas-lms,skmezanul/canvas-lms,tgroshon/canvas-lms,kyroskoh/canvas-lms,leftplusrightllc/canvas-lms,utkarshx/canvas-lms,SwinburneOnline/canvas-lms,eCNAP/CANVAS,jay3126/canvas-lms,venturehive/canvas-lms,Rvor/canvas-lms,kyroskoh/canvas-lms,HotChalk/canvas-lms,ShreniiNepal/shrenii_lmp,ShreniiNepal/shrenii_lmp,instructure/canvas-lms,leftplusrightllc/canvas-lms,narigone/canvas,kyroskoh/canvas-lms,narigone/canvas,sdeleon28/canvas-lms,dgynn/canvas-lms,whalejasmine/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,AndranikMarkosyan/lms,fronteerio/canvas-lms,fronteerio/canvas-lms,instructure/canvas-lms,Jyaasa/canvas-lms,redconfetti/canvas-lms,wrdsb/canvas-lms,va7map/canvas-lms,djbender/canvas-lms,narigone/canvas,whalejasmine/canvas-lms,snehakachroo1/LSI_replica,instructure/canvas-lms,snehakachroo1/LSI_replica,antoniuslin/canvas-lms,eCNAP/CANVAS,shidao-fm/canvas-lms,skmezanul/canvas-lms,HotChalk/canvas-lms,eCNAP/CANVAS,greyhwndz/canvas-lms,Rvor/canvas-lms,sdeleon28/canvas-lms,antoniuslin/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,shidao-fm/canvas-lms,whalejasmine/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,efrj/canvas-lms,va7map/canvas-lms,utkarshx/canvas-lms,roxolan/canvas-lms,greyhwndz/canvas-lms,instructure/canvas-lms,wrdsb/canvas-lms,SwinburneOnline/canvas-lms,HotChalk/canvas-lms,utkarshx/canvas-lms,matematikk-mooc/canvas-lms