lib/download.c: debug: print url info only if it's available.
lib/download.c: debug: print url info only if it's available.

datenwolf/xbps,ebfe/xbps,datenwolf/xbps,ebfe/xbps,datenwolf/xbps,stpx/xbps,ebfe/xbps,stpx/xbps,stpx/xbps