Hi,
thanks for maintaining this mod.
As I wrote to you in a mail previously, the window needed to view the achievements doesn't open for me and KSP.log has these error lines. This happens both with the spacedock release and when building from source. The error message to me indicates, that earnedAchievements is null here (as .Count() is called on it). On my end, the instructions in this if are not executed, therefore earnedAchievements stays null afterwards. Now I'm not sure if this is still something on my end or not, but perhaps this can help with fixing things.