For your reference,
According to your screen shot you selected a Description with an empty Address. You can assume that this is meant to be a title block due to the description being the name of the gun and the following descriptions sub categories of the gun. When you selected the description it entered itself into the write section with no address, one would assume people would realise. You attempted to write nothing into the games code, you were returned with the error 'Index was out of range'. If you search this error on MSDN you will find the definition of "The exception that is thrown when an attempt is made to access an element of an array with an index that is outside the bounds of the array. This class cannot be inherited.". From this you can assume that the way this program was coded was with arrays, and when an empty field is selected its index is not handled and then returns an error.
Hopefully this all makes sense and can give you a bit of logic to why you got that error.
The Following User Says Thank You to NadeHouse For This Useful Post: