If a field is mapped to another through the Left or Right method and the amount of characters to keep left or right is greater than the length of a string in the source row, the target row will append None instead. Seen below in the first and second row.
If a field is mapped to another through the Left or Right method and the amount of characters to keep left or right is greater than the length of a string in the source row, the target row will append None instead. Seen below in the first and second row.![leftbug](https://user-images.githubusercontent.com/29782875/29280369-d75ac2a4-80cf-11e7-92a7-2d7cbe201a92.gif)
EDIT: Seems to also happen with Substring