make macro expansion ignore empty ASTs
make macro expansion ignore empty ASTs

Fixes RT #115506.

awwaiid/rakudo,pmurias/rakudo,softmoth/rakudo,retupmoca/rakudo,jonathanstowe/rakudo,sergot/rakudo,cognominal/rakudo,Leont/rakudo,paultcochrane/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,cognominal/rakudo,jonathanstowe/rakudo,skids/rakudo,sergot/rakudo,nbrown/rakudo,salortiz/rakudo,nunorc/rakudo,rakudo/rakudo,nbrown/rakudo,teodozjan/rakudo,rakudo/rakudo,labster/rakudo,samcv/rakudo,dwarring/rakudo,cognominal/rakudo,azawawi/rakudo,nunorc/rakudo,skids/rakudo,teodozjan/rakudo,tony-o/rakudo,pmurias/rakudo,awwaiid/rakudo,ab5tract/rakudo,sjn/rakudo,tony-o/rakudo,MasterDuke17/rakudo,laben/rakudo,ab5tract/rakudo,nunorc/rakudo,ungrim97/rakudo,niner/rakudo,labster/rakudo,laben/rakudo,awwaiid/rakudo,zostay/rakudo,dwarring/rakudo,LLFourn/rakudo,raydiak/rakudo,lucasbuchala/rakudo,paultcochrane/rakudo,tony-o/rakudo,b2gills/rakudo,tbrowder/rakudo,zostay/rakudo,ungrim97/rakudo,b2gills/rakudo,MasterDuke17/rakudo,ab5tract/rakudo,rakudo/rakudo,samcv/rakudo,raydiak/rakudo,retupmoca/rakudo,raydiak/rakudo,laben/rakudo,usev6/rakudo,salortiz/rakudo,azawawi/rakudo,cognominal/rakudo,rjbs/rakudo,nbrown/rakudo,rjbs/rakudo,samcv/rakudo,dankogai/rakudo,labster/rakudo,niner/rakudo,Leont/rakudo,ugexe/rakudo,teodozjan/rakudo,zostay/rakudo,nbrown/rakudo,samcv/rakudo,cygx/rakudo,labster/rakudo,softmoth/rakudo,b2gills/rakudo,dankogai/rakudo,tony-o/deb-rakudodaily,laben/rakudo,ab5tract/rakudo,azawawi/rakudo,LLFourn/rakudo,paultcochrane/rakudo,dankogai/rakudo,usev6/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,retupmoca/rakudo,tony-o/deb-rakudodaily,labster/rakudo,salortiz/rakudo,sergot/rakudo,softmoth/rakudo,salortiz/rakudo,retupmoca/rakudo,LLFourn/rakudo,tony-o/deb-rakudodaily,zhuomingliang/rakudo,sjn/rakudo,nbrown/rakudo,tony-o/rakudo,zhuomingliang/rakudo,ungrim97/rakudo,Gnouc/rakudo,sjn/rakudo,samcv/rakudo,tony-o/rakudo,pmurias/rakudo,nbrown/rakudo,softmoth/rakudo,ugexe/rakudo,labster/rakudo,Leont/rakudo,dankogai/rakudo,salortiz/rakudo,paultcochrane/rakudo,tony-o/deb-rakudodaily,tbrowder/rakudo,tony-o/deb-rakudodaily,usev6/rakudo,ugexe/rakudo,rakudo/rakudo,azawawi/rakudo,Gnouc/rakudo,cygx/rakudo,zhuomingliang/rakudo,b2gills/rakudo,Gnouc/rakudo,b2gills/rakudo,lucasbuchala/rakudo,skids/rakudo,Gnouc/rakudo,nunorc/rakudo,Gnouc/rakudo,zhuomingliang/rakudo,ab5tract/rakudo,sjn/rakudo,Leont/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,dankogai/rakudo,tbrowder/rakudo,azawawi/rakudo,zostay/rakudo,tbrowder/rakudo,sjn/rakudo,salortiz/rakudo,pmurias/rakudo,cognominal/rakudo,niner/rakudo,ungrim97/rakudo,tony-o/rakudo,rjbs/rakudo,tony-o/deb-rakudodaily,awwaiid/rakudo,dwarring/rakudo,sergot/rakudo,lucasbuchala/rakudo,tony-o/deb-rakudodaily,dwarring/rakudo,ugexe/rakudo,tbrowder/rakudo,LLFourn/rakudo,lucasbuchala/rakudo,niner/rakudo,skids/rakudo,Gnouc/rakudo,raydiak/rakudo,ungrim97/rakudo,jonathanstowe/rakudo,usev6/rakudo,cygx/rakudo,cygx/rakudo,softmoth/rakudo,cygx/rakudo,rakudo/rakudo,tbrowder/rakudo,skids/rakudo,usev6/rakudo,LLFourn/rakudo,rakudo/rakudo,awwaiid/rakudo,paultcochrane/rakudo,ugexe/rakudo,teodozjan/rakudo