Prevent fadeOut from being called twice
Prevent fadeOut from being called twice

Prevent fadeOut from being called twice if the user clicks the
notification while it hasn't finished the fadeIn animation.

Fixes _this.$() is undefined error.

https://app.getsentry.com/scrapinghub/portia/group/71048791/

hanicker/portia,NoisyText/portia,PrasannaVenkadesh/portia,SouthStar/portia,Youwotma/portia,naveenvprakash/portia,Youwotma/portia,NoisyText/portia,sntran/portia,livepy/portia,sntran/portia,PrasannaVenkadesh/portia,sntran/portia,Suninus/portia,hanicker/portia,NicoloPernigo/portia,NoisyText/portia,chennqqi/portia,livepy/portia,chennqqi/portia,amikey/portia,Suninus/portia,naveenvprakash/portia,NoisyText/portia,Suninus/portia,anjuncc/portia,Suninus/portia,anjuncc/portia,pombredanne/portia,amikey/portia,PrasannaVenkadesh/portia,anjuncc/portia,pombredanne/portia,hanicker/portia,NicoloPernigo/portia,chennqqi/portia,pombredanne/portia,SouthStar/portia,NicoloPernigo/portia,SouthStar/portia,livepy/portia,naveenvprakash/portia,Youwotma/portia,livepy/portia,hanicker/portia,SouthStar/portia,anjuncc/portia,amikey/portia,PrasannaVenkadesh/portia,NicoloPernigo/portia,pombredanne/portia,amikey/portia,naveenvprakash/portia,Youwotma/portia,sntran/portia,chennqqi/portia