Error when calling plot()

[kcsanad98]

Hi!

The method for saving mentioned in issue #68 stopped working in version 2.1.13. It's working fine in 2.1.11 though.
The error is thrown when calling the plot() function.
This can be reproduced with the following code:

library(rAmCharts)

data <- data.frame(
  label = c("label1", "label2"),
  value = c(1, 2),
  stringsAsFactors = FALSE
)

rAmCharts::amPie(data = data) -> widget

htmlwidgets::saveWidget(
  widget = plot(widget),
  file = "widget.html"
)

It gives the following error message:

Error in as.double(y) : cannot coerce type 'S4' to vector of type 'double'