Fix check for empty sources
Fix check for empty sources

pearsonlab/thunder,broxtronix/thunder,mikarubi/thunder,mikarubi/thunder,oliverhuangchao/thunder,j-friedrich/thunder,jwittenbach/thunder,zhwa/thunder,kcompher/thunder,oliverhuangchao/thunder,kunallillaney/thunder,thunder-project/thunder,zhwa/thunder,pearsonlab/thunder,j-friedrich/thunder,poolio/thunder,kcompher/thunder,poolio/thunder,broxtronix/thunder,kunallillaney/thunder