aurelius::pfa for rpart (method = "anova") issue argument is length zero

Trying to call pfa.rpart on a regression tree (instead of a classification tree as in the example) gives the following

```r 
model <- rpart::rpart(Sepal.Length ~ ., data=iris)
model_as_pfa <- pfa(model)
```
Console:
```
Error in if (!is.na(node$SplitVar)) { : argument is of length zero
```

Please advise.