You have not assigned a GridView to GridViewUserScraps - it is a null value, so when you try to access it's DataSource property, you get an exception. Look elsewhere in your code, and find where it is declared - then work out what you meant to do with it!
And please, don't do things like that: Check your query strings before you try to use them, and do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead. This is particularly important when dealing with web based code, when your database could be destroyed from the other side of the world.