Remove empty line from CMakeLists.txt.
Remove empty line from CMakeLists.txt.

hsorby/libcellml,cellml/libcellml,nickerso/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,cellml/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml,cellml/libcellml