Fixing a bug generated if concatenating null strings
Fixing a bug generated if concatenating null strings

cga-harvard/hypermap,cga-harvard/HHypermap,jmwenda/hypermap,cga-harvard/HHypermap,cga-harvard/HHypermap,cga-harvard/hypermap,cga-harvard/HHypermap,jmwenda/hypermap,jmwenda/hypermap,cga-harvard/hypermap,jmwenda/hypermap,cga-harvard/hypermap