Error: Example Set is Empty
I'm trying to cluster an exampleset with some missing values. I'm using "impute Missing Values" with the k-NN inner operator. I can see (with breakpoints) that the exampleset is fine right until it reaches the Impute node, but the inner k-NN operator apparently receives an empty example set. I've set the attribute selection filter to "all" for the impute node including special attributes (I only have an id attribute), and I've checked the boxes for "iterate" and "learn on complete cases".
I'm not sure what's going on. The process was working fine until a day ago but when I tried to execute it today, it's throwing me the empty example set error during missing value imputation. I've attached the process xml.