Well no, it's a simple javascript that checks if the field contains a file or not. If you've selected a file it should simply proceed and the only must is a game file, the image file isn't mandatory.
Either way I've adjusted the check a little bit. Could you please try again and tell me if it works now?
Oh and just to get things clear for me. Did you get that message before you actually uploaded the game or after you tried to upload it. Meaning did you get it when you pressed the actual Upload button and saw the animation of a game upload or was it when you had just selected your game file and clicked Continue?
"The absence of rules is the enemy of art." ~Orson Wells
