NumberFormat Exception fix.
Merge pull request #10 from hangum/1.4.2

1.4.2
bug fix #537 - https://github.com/hangum/TadpoleForDBTools/issues/537
Merge branch '1.4.2' of https://github.com/jeongjaehong/TadpoleForDBTools.git into 1.4.2
Merge pull request #539 from jeongjaehong/1.4.2

bug fix #537