fix(accordion): coerce to boolean
fix(accordion): coerce to boolean

- Coerce `toggleClass` argument to boolean due to jQuery ignoring
  `undefined`

Closes #4385

jordangraft/bootstrap,caoruiy/bootstrap,spadgett/bootstrap,codedogfish/angular-ui-bootstrap,bikegriffith/bootstrap,mabi/bootstrap,wesleycho/bootstrap,burlhock/bootstrap,themifycloud/bootstrap,pdsoftplan/bootstrap,nathan-j-brenner/bootstrap-1,parikmaher534/bootstrap,kemapak/bootstrap,tmcgee123/bootstrap,connyay/bootstrap,ksheedlo/bootstrap,JDeuker/bootstrap,burlhock/bootstrap,rasulnz/bootstrap,shootermv/bootstrap,vsternbach/bootstrap,stereocilia/bootstrap,karelcallens/bootstrap,kongx73/bootstrap,shiftagent/ui-bootstrap,kirning/bootstrap-1,rhamid/bootstrap-1,SystemDisc/bootstrap,SimilarWeb/bootstrap,Lincoln-xzc/angular-ui-bootstrap,deeg/bootstrap,nathan-j-brenner/bootstrap-1,dsisejkovic/bootstrap,leyanlo/bootstrap,SatvikPurohit/bootstrap,rodrigues-daniel/bootstrap,guaido79/bootstrap,benhalverson/bootstrap,byronigoe/bootstrap,maoli1110/bootstrap,ehteshamkafeel/bootstrap,thalen/bootstrap,justin-john/bootstrap-1,maoli1110/bootstrap,infowrap/bootstrap,yubin-huang/bootstrap,fabg21/bootstrap,madhudskumar/bootstrap,Kpler/bootstrap,icfantv/bootstrap,yubin-huang/bootstrap,benhalverson/bootstrap,cdrewery/bootstrap,karelcallens/bootstrap,gorork/bootstrap,yjukaku/bootstrap,jordangraft/bootstrap,edivancamargo/bootstrap,Gailby/bootstrap,deeg/bootstrap,SystemDisc/bootstrap,finkcloud/bootstrap,mikesavior/bootstrap,pdsoftplan/bootstrap,Xephi/bootstrap,jaydiablo/bootstrap,carlosjunior/bootstrap,Schibum/bootstrap,cgvarela/bootstrap-1,JonFerrera/ui-bootstrap,WXwangxin/bootstrap,angular-ui/bootstrap,leyanlo/bootstrap,zhaokunfay/bootstrap,linuxb/bootstrap,mikesavior/bootstrap,azahreba/bootstrap,mabi/bootstrap,bikegriffith/bootstrap,Xephi/bootstrap,alokpradhan/bootstrap,kmccaw/bootstrap,angular-ui/bootstrap,WXwangxin/bootstrap,Nekle/bootstrap,GirishKumrawat/bootstrap,Foxandxss/bootstrap,gorork/bootstrap,voyagecontrol/bootstrap,edivancamargo/bootstrap,carlosjunior/bootstrap,byronigoe/bootstrap,liqingzhu/bootstrap,kirning/bootstrap-1,dsisejkovic/bootstrap,Schibum/bootstrap,rajesh-frontendengineer/bootstrap-1,yukisan/bootstrap,Zazulei/bootstrap,liiza/bootstrap,linuxvom/bootstrap,justin-john/bootstrap-1,mufl1h/bootstrap,infowrap/bootstrap,oliversalzburg/bootstrap,elancom/bootstrap-1,wesleycho/bootstrap,madhudskumar/bootstrap,sullivanpt/bootstrap,fabg21/bootstrap,vsternbach/bootstrap,finkcloud/bootstrap,oliversalzburg/bootstrap,kongx73/bootstrap,fpipita/bootstrap,Vreasy/bootstrap,shadowdaw/bootstrap,KingMario/bootstrap-1,BookingBug/bootstrap,linuxvom/bootstrap,stereocilia/bootstrap,vfiles/bootstrap,universsky/bootstrap-1,eduncan26/bootstrap,Foxandxss/bootstrap,matteopic/bootstrap,vfiles/bootstrap,caoruiy/bootstrap,BookingBug/bootstrap,RobJacobs/bootstrap,linuxb/bootstrap,shootermv/bootstrap,pmalikbtech/bootstrap,woshiyigebing/bootstrap,rodrigues-daniel/bootstrap,connyay/bootstrap,thalen/bootstrap,rajesh-frontendengineer/bootstrap-1,guaido79/bootstrap,cesarmarinhorj/AngularJS-bootstrap,eduncan26/bootstrap,GirishKumrawat/bootstrap,Servoy/bootstrap,codedogfish/angular-ui-bootstrap,Vreasy/bootstrap,kmccaw/bootstrap,looker/bootstrap,jaydiablo/bootstrap,SimilarWeb/bootstrap,lancerushing/bootstrap,lancerushing/bootstrap,voyagecontrol/bootstrap,RobJacobs/bootstrap,Gailby/bootstrap,rasulnz/bootstrap,christor/bootstrap,woshiyigebing/bootstrap,franzherzog/bootstrap,shiftagent/ui-bootstrap,liiza/bootstrap,ksheedlo/bootstrap,atulc007/bootstrap-1,realityking/ui-bootstrap,KingMario/bootstrap-1,yjukaku/bootstrap,christor/bootstrap,shadowdaw/bootstrap,franzherzog/bootstrap,fpipita/bootstrap,universsky/bootstrap-1,cgvarela/bootstrap-1,292388900/bootstrap,azahreba/bootstrap,pireerliu/bootstrap,icfantv/bootstrap,sullivanpt/bootstrap,292388900/bootstrap,JonFerrera/ui-bootstrap,shihang0001/bootstrap,tmcgee123/bootstrap,zhaokunfay/bootstrap,pireerliu/bootstrap,matteopic/bootstrap,Anirudhk94/bootstrap,rhamid/bootstrap-1,themifycloud/bootstrap,thomassorensen/bootstrap,Kpler/bootstrap,looker/bootstrap,alokpradhan/bootstrap,pmalikbtech/bootstrap,atulc007/bootstrap-1,JDeuker/bootstrap,mufl1h/bootstrap,kemapak/bootstrap,Anirudhk94/bootstrap,Servoy/bootstrap,tobigun/bootstrap,Zazulei/bootstrap,elancom/bootstrap-1,Lincoln-xzc/angular-ui-bootstrap,filso/bootstrap,spadgett/bootstrap,Nekle/bootstrap,SatvikPurohit/bootstrap,liqingzhu/bootstrap,parikmaher534/bootstrap,benhalverson/bootstrap,cdrewery/bootstrap,benhalverson/bootstrap,cesarmarinhorj/AngularJS-bootstrap,thomassorensen/bootstrap,tobigun/bootstrap,shihang0001/bootstrap,filso/bootstrap,inoxis91/bootstrap,ehteshamkafeel/bootstrap,inoxis91/bootstrap,realityking/ui-bootstrap,davious/angular-ui-bootstrap,yukisan/bootstrap,davious/angular-ui-bootstrap