The game mode will never be null. The point of the defaulted key system (VanillaData.GAMEMODE) is that you can assign default values. So this branch will never be executed.

The default value for gamemode is survival: https://github.com/VanillaDev/Vanilla/blob/master/src/main/java/org/spout/vanilla/plugin/data/VanillaData.java#L64