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Object reference not set to an instance of an object
Void Update(Microsoft.Xna.Framework.GameTime)
Saved easy mode beatmap as Normal and was editing. I switched the snap divisor to quarter beats to put in a slider, extended it, and switched the snap divisor back to half beats. Replayed it once to make sure that the beat was correct. I wanted to change the position of the slider so I selected the tail end of it and tried to drag it around to the right position as the head end was in the spot I wanted. The editor decided to snap it to half-beats so I hit CTRL-Z to undo.
Tada! Error message.