nearPoints() and brushedPoints() don't work with NA panels

[cpsievert]

Hover over the third panel. Discovered during review of #2668 (pretty sure this bug has always existed)

library(shiny)
library(ggplot2)

ui <- basicPage(
  plotOutput("plot", hover = hoverOpts("hover")),
  verbatimTextOutput("nearPoint")
)

server <- function(input,output){
  
  dat <- data.frame(
    x = 1:3,
    y = 1:3,
    z = c("a", "b", NA)
  )
  
  output$plot <- renderPlot({
    ggplot(dat, aes(x, y)) + 
      geom_point() +
      facet_wrap(~z)
  })
  
  output$nearPoint <- renderPrint({
    if(!is.null(coordinfo <- input$hover)){
      nearPoints(dat, coordinfo, threshold = 15, maxpoints = 1)
    }
  })
}

shinyApp(ui, server)