add nil user fix to create method

Hey chris, whenever I tried to create a new question it would throw me a no method error on "questions," so I realized you would return nil on your @user when you shoveled the questions into the user. So all i did was append your if statement with "&& @user" so that it no longer cares if its a user. Then i put some logic into your users show controller to get you started on showing all the questions that you are associating to the user when you check out the user's show page.