I will do at least one more update to this project so will add the check for the other enemies damaging HP. Will also be adding an MP meter that is filled when performing melee kills. And then the ice wave will only be available with sufficient MP.
As for the error, its because the iceblock object is not associated with the freezeObj variable on the camera. This was intentional as it was making an unwanted ice block appear. Long term, I will need to come up with a proper solution. However, I don't think the error should prevent the project or resulting exe file from running.