missing default luminance source if null is given
missing default luminance source if null is given

git-tfs-id: [https://tfs.codeplex.com/tfs/TFS05/]$/ZXingNet/trunk;C81743

micjahn/ZXing.Net,DHMechatronicAG/ZXing.Net,bsoja/ZXing.Net,bsoja/ZXing.Net,DHMechatronicAG/ZXing.Net,bsoja/ZXing.Net,micjahn/ZXing.Net,micjahn/ZXing.Net,DHMechatronicAG/ZXing.Net