Fix condition for testing if a package description exists.
Fix condition for testing if a package description exists.

xentec/dub,grogancolin/dub,jelmansouri/dub,Abscissa/dub-data-mod,Flamaros/dub,Geod24/dub,rjframe/dub,y12uc231/dub,p0nce/dub,dreamsxin/dub,alexeibs/dub,nazriel/dub,schuetzm/dub,gedaiu/dub,Abscissa/dub,jeanbaptistelab/dub,D-Programming-Language/dub