xbps_repo_key_import: check that returned hex fingerprint is not NULL.
xbps_repo_key_import: check that returned hex fingerprint is not NULL.

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