R shiny: Cannot delete last value in SelectizeInput - r

Question

I have a very simple question:
Why is it in the following code not possible to remove the last entered value in SelectizeInput? E.g. I entered "a" "b" & "c" and I want to delete them all afterwards from the SelectizeInput. Why is it no possible to remove the last remaing value from SelectizeInput?
library(shiny)
ui <- bootstrapPage(
textInput(inputId = "txtinput", label = "Insert label", value = "", placeholder = ""),
actionButton(inputId = "actbtn", label = "Add label"),
uiOutput('selctInput')
)
server <- function(input, output, session){
#Create reactive values
rv <- reactiveValues()
#When Button is clicked..
observeEvent(input$actbtn, {
#Save value in a reactiveValues list
rv$new.label <- input$txtinput
#Collect all entries from text input
rv$labels <- c(rv$labels, rv$new.label)
#Clear textinput
updateTextInput(session, "txtinput", value = "")
})
#When selectizeInput changes...
observeEvent(input$selctInput, {
#Why is it not possible to completely empty selectizeInput? The last value just remains.
rv$labels <- input$selctInput
print(input$selctInput)
})
#Add selectizeInput to UI
output$selctInput <- renderUI({
selectizeInput(inputId = "selctInput", label= "Reorder / delete labels",
choices = rv$labels,
selected = rv$labels, multiple=TRUE,
options = list(plugins = list('remove_button', 'drag_drop')))
})
}
shinyApp(ui, server)

Answer 1

You just need to add ignoreNULL = FALSE to your observeEvent so that it "reacts" to the NULL value
#When selectizeInput changes...
observeEvent(input$selctInput, {
#Why is it not possible to completely empty selectizeInput? The last value just remains.
rv$labels <- input$selctInput
print(input$selctInput)
}, ignoreNULL = FALSE)
Update:
After finding this link https://gist.github.com/pvictor/ee154cc600e82f3ed2ce0a333bc7d015 there seems to be a far simpler approach:
library(shiny)
ui <- fluidPage(
selectizeInput("select", "Select", c(),
multiple = TRUE, options = list(
'plugins' = list('remove_button'),
'create' = TRUE,
'persist' = FALSE)
),
textOutput("out")
)
server <- function(input, output){
output$out <- renderText({
input$select
})
}
shinyApp(ui, server)