fix(select): don't process navigation keys with multiple select
fix(select): don't process navigation keys with multiple select

Keyboard navigation/selection is not implemented for multiple selects, so we need to check if select type is not multiple before handling cursor keypresses.
This should really be handled by implementing the keyboard navigation, but for now, just a quick fix.

Fixes #1521

clight92/angular-strap,bstruthers/angular-strap,grrseguin/angular-strap,Quivr/angular-strap,vmlf01/angular-strap,zanebenefits/angular-strap,atulsaini/angular-strap,Mindfor/angular-strap,skolsuper/angular-strap,capaj/angular-strap,AlfiyaZi/angular-strap,kkirsche/angular-strap,moodpo/angular-strap,zanebenefits/angular-strap,bbloomf/angular-strap,renyaoxiang/angular-strap,qimenxiaozi/angular-strap,palortoff/angular-strap,keshavwork/angular-strap,lightswitch05/angular-strap,lookfirst/angular-strap,moodpo/angular-strap,viikas/angular-strap,axschech/angular-strap,vmlf01/angular-strap,cloudcck/angular-strap,andras-tim/angular-strap,palortoff/angular-strap,grrseguin/angular-strap,RatanPaul/angular-strap,lightswitch05/angular-strap,sander-v-bergen/angular-strap,rigup/angular-strap,siddharta1337/angular-strap,Mindfor/angular-strap,kenyus/angular-strap,capaj/angular-strap,alimek/angular-strap,AlfiyaZi/angular-strap,grushikhin/angular-strap,kenyus/angular-strap,aaronroberson/angular-strap,RatanPaul/angular-strap,lookfirst/angular-strap,alimek/angular-strap,evillemez/angular-strap,akuznetsov-gridgain/angular-strap,lewis-ing/angular-strap,kkirsche/angular-strap,viikas/angular-strap,JsonChiu/angular-strap,keshavwork/angular-strap,mgcrea/angular-strap,cloudcck/angular-strap,khellang/angular-strap,evillemez/angular-strap,sander-v-bergen/angular-strap,wangjun/angular-strap,aaronroberson/angular-strap,terguevarra/angular-strap,clight92/angular-strap,edivancamargo/angular-strap,siddharta1337/angular-strap,uidoor/angular-strap,terguevarra/angular-strap,michaelfdeberry/angular-strap,axschech/angular-strap,mgcrea/angular-strap,mattgoldspink/angular-strap,episodeyang/angular-strap,uidoor/angular-strap,rigup/angular-strap,mattgoldspink/angular-strap,grushikhin/angular-strap,wyzellak/angular-strap,skolsuper/angular-strap,wyzellak/angular-strap,bstruthers/angular-strap,edivancamargo/angular-strap,renyaoxiang/angular-strap,michaelfdeberry/angular-strap,khellang/angular-strap,JsonChiu/angular-strap,wangjun/angular-strap,episodeyang/angular-strap,lewis-ing/angular-strap,atulsaini/angular-strap,bbloomf/angular-strap,Quivr/angular-strap,qimenxiaozi/angular-strap,andras-tim/angular-strap,akuznetsov-gridgain/angular-strap