When clicking on scroll bar after entering value in input box, an “Invalid use of Null” warning message pops up and crashes the program.

After entering a value in an input box, users are strongly advised to press “Tab” or “Enter” on their keyboards.  Avoid using the mouse to click away to another input box, tab or scroll bar.  The mouse click may inadvertently create a null entry in the user file and result in crashing the program due to invalid use of null.