keep the REF field not empty
keep the REF field not empty

ShujiaHuang/AsmVar,ShujiaHuang/AsmVar,bioinformatics-centre/AsmVar,bioinformatics-centre/AsmVar,bioinformatics-centre/AsmVar,ShujiaHuang/AsmVar,ShujiaHuang/AsmVar,bioinformatics-centre/AsmVar,bioinformatics-centre/AsmVar,ShujiaHuang/AsmVar,ShujiaHuang/AsmVar,bioinformatics-centre/AsmVar