[Bug] visitor fails for empty arguments

[EagleoutIce]

We do need some kind of

# if the node does not have a 'type', return
if (!"type" %in% names(node)) {
  return()
}

guard!

[EagleoutIce]

The named check has to be guarded as well:

RFunctionCall = {
if ('named' %in% names(node) && node$named) {
  visit_node(node$functionName, callback)
} else {
  visit_node(node$calledFunction, callback)
}
visit_nodes(node$arguments, callback)
},