fix(dropdown): adjust for better compatibility with universal
fix(dropdown): adjust for better compatibility with universal

Closes #1883

fbasso/ng-bootstrap,fbasso/ng-bootstrap,jnizet/ng-bootstrap,maxokorokov/core,mschoudry/ng-bootstrap,ng-bootstrap/core,ktriek/ng-bootstrap,benouat/ng-bootstrap,ng-bootstrap/core,pkozlowski-opensource/core,ktriek/ng-bootstrap,maxokorokov/core,ng-bootstrap/ng-bootstrap,ktriek/ng-bootstrap,benouat/ng-bootstrap,pkozlowski-opensource/core,maxokorokov/core,Foxandxss/ng-bootstrap,pkozlowski-opensource/core,benouat/ng-bootstrap,ktriek/ng-bootstrap,ng-bootstrap/core,ng-bootstrap/ng-bootstrap,jnizet/ng-bootstrap,mschoudry/ng-bootstrap,ng-bootstrap/ng-bootstrap,fbasso/ng-bootstrap,benouat/ng-bootstrap,Foxandxss/ng-bootstrap,jnizet/ng-bootstrap,mschoudry/ng-bootstrap,ng-bootstrap/ng-bootstrap,maxokorokov/core,Foxandxss/ng-bootstrap,fbasso/ng-bootstrap,jnizet/ng-bootstrap