reproducible bug case for ggvis

server.r

library(dplyr)
library(ggvis)
library(shiny)
shinyServer(function(input, output, session) {
  
  session$onSessionEnded(function() {
    stopApp()
  })
  mtcars$cyl <- factor(mtcars$cyl, levels = c(4L,6L, 8L))
  
  reactive({
    mtcars %>% 
      group_by(cyl) %>%
      ggvis(~wt, ~mpg) %>% 
      group_by(cyl) %>% 
      layer_points(fill = ~cyl, size := 12) %>% 
      set_options(width = "auto", height = "200px", resizable=FALSE)
  }) %>% bind_shiny("plot1")
  
  reactive({
    mtcars %>% 
      group_by(cyl) %>%
      ggvis(~wt, ~hp) %>% 
      group_by(cyl) %>% 
      layer_points(fill = ~cyl, size := 12) %>% 
      set_options(width = "auto", height = "200px", resizable=FALSE)
  }) %>% bind_shiny("plot2")
})

ui.r

library(dplyr)
library(ggvis)
library(shiny)
shinyUI(
  navbarPage("Demo", 
             position = "static-top",
             fluid = F,
            tabPanel("Demo",class="active",
                      sidebarLayout(
                        sidebarPanel(
                          ggvisOutput("plot1"),
                          ggvisOutput("plot2")
                        ),
                        mainPanel()
                        ))
  ))