HTML Widgets; Account Financial control; Error returned if Standard Transaction is removed instead of set to $0

In the Account Financial Control (used in the New Account wizard, for example), if a User selected a Standard Transaction value cell and pressed "Delete" on their keyboard, an error would be returned and all Standard Transactions would be removed.

This behaviour was incorrect, and now instead of removing the value as it did before (which caused the error), the cell will be reset to 0. If the User wants to remove the Standard Transaction completely, the row should be selected and the delete button beneath the grid (it has a red cross icon) should be clicked.