fill + opacity in layer_densities() causes crash in ggvis

ggvisdensitycrash.R

# Started from here, an example from Hadley Wickham in the google groups https://groups.google.com/forum/#!topic/ggvis/AJZCdjFcNaE. 
# Using R 3.2.1 x86_64, ggvis 0.4.2. 

cocaine %>%
  ggvis( ~ potency, ~ price) %>%
  filter(state %in% eval(input_checkboxgroup(c("IA", "MN", "WI"),
                                             selected = "WI"))) %>%
  layer_points(fill = ~ state, size := 50, opacity := 0.5) 
  
# This works fine and evals the way one would expect.

# I changed to densities:

cocaine %>%
  ggvis( ~ potency, ~ price) %>%
  filter(state %in% eval(input_checkboxgroup(c("IA", "MN", "WI"),
                                             selected = "WI"))) %>%
  layer_densities(fill = ~ state, opacity := 0.5) 
  
This vis starts up fine, displays the checkboxes, etc.  
However, when I try to add/change the state, the whole vis crashes.
and throws this error message:

"Warning: Unhandled error in observer: object 'state' not found
observe({
    data_reactive <- data_table[[data_name]]
    session$sendCustomMessage("ggvis_data", list(plotId = id, 
        name = data_name, value = as.vega(data_reactive(), data_name)))
})
Warning: Unhandled error in observer: object 'state' not found
observe({
    data_reactive <- data_table[[data_name]]
    session$sendCustomMessage("ggvis_data", list(plotId = id, 
        name = data_name, value = as.vega(data_reactive(), data_name)))
})
Warning: Unhandled error in observer: object 'state' not found
observe({
    for (name in names(data_table)) {
        data_table[[name]]()
    }
    session$sendCustomMessage("ggvis_command", list(plotId = id, 
        command = "update"))
})
ERROR: [on_request_read] connection reset by peer"