don't add a tag if there is no source information
don't add a tag if there is no source information

anddann/soot,mbenz89/soot,plast-lab/soot,cfallin/soot,mbenz89/soot,anddann/soot,plast-lab/soot,cfallin/soot,cfallin/soot,cfallin/soot,xph906/SootNew,xph906/SootNew,anddann/soot,xph906/SootNew,mbenz89/soot,xph906/SootNew,plast-lab/soot,mbenz89/soot,anddann/soot