check for empty string parameters
check for empty string parameters

test plan
* you should be able to pass 'all terms' on a 
report with a term selector

Change-Id: Iaf8eb3c59f2818233477c490b3a030fc24ebfbd4
Reviewed-on: https://gerrit.instructure.com/16953
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Brad Humphrey <9233b6f5388d6867a2a7be14d8b4ba53c86cfde2@instructure.com>
QA-Review: Brad Humphrey <9233b6f5388d6867a2a7be14d8b4ba53c86cfde2@instructure.com>

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