Added default value for missing alert subject args values
Added default value for missing alert subject args values

jetyang2005/elastalert,dvopsway/elastalert,talyian/elastalert,iamrudra/elastalert,jetyang2005/elastalert,thomdixon/elastalert,rprabhat/elastalert,Yelp/elastalert,ltagliamonte/elastalert,lytics/elastalert,mash0304/elastalert,amoennin/elastalert,kkoppel/elastalert,saltukalakus/elastalert,saltukalakus/elastalert,brianparry/elastalert,jetyang2005/elastalert,rarescosma/elastalert,rounds/elastalert,AlphaStaxLLC/elastalert,gbenoit79/elastalert,megancarney/elastalert