renderLeaflet: legend is not rendered in shiny

Question

Using the renderLeaflet (following codes), I am trying to create an interactive map within shiny. I want the map to be updated based on users selections of age group, sex, and year. When age group=60 and sex=both sexes and year= 2010 are selected, everything looks great (please see this screen shot). However, when the other age groups are selected, the legend remains unchanged and is not rendered (Please see the second screen shot). Here is my code:

mapdata_ <- reactive ({

    nhmap$Per <- round(nhmap$Per, 1) 

    out_map <- nhmap %>%
        filter (
            Age_Group %in% input$Age_Group_map,
            Sex %in% input$sex_map,
            Year %in% input$Year_map)

    return(out_map)
})

output$int_map <- renderLeaflet ({

    leaflet (mapdata_(),
             pal8 <- c("#FFFFE5", "#D9F0A3", "#78C679", "#006837") ,
             pal <- colorBin(palette = pal8, domain = nhmap$Per, bins=4, right =FALSE, na.color = "#808080",  alpha = FALSE, reverse = F)
            ) %>%

    addProviderTiles("CartoDB.Positron") %>% 
    clearControls() %>%
    clearShapes()%>%
    addPolygons(fillColor = ~pal(Per),
                stroke=T,
                weight=1,
                smoothFactor=0.2,
                fillOpacity = 1,
                color="black",
                popup=~paste(NAME,"<br>",input$sex_map,
                    input$Age_Group_map,"=",Per,"%"),
                highlightOptions = highlightOptions(color = "red",
                    weight = T,
                    bringToFront = T),
                label=~NAME) %>%
    addTiles() %>%
    setView(-82.706838, 40.358615, zoom=7) %>%
    addLegend(position = "bottomright",
        values = ~pal(Per),
        pal = pal,
        title = (paste("%",input$Age_Group_map, input$sex_map, "in", input$Year_map)) ,
        labFormat = labelFormat())
})