Remove fake item containing an external hyperlink in a navbar menu

In a dropdown menu, there is a blank line (a fake item) above each item containing a <a> tag. I don't know how to remove it. I tested several solutions but nothing worked. @benoit.genot any idea?

An example where the problem appears above items 3 and 4.

library(shiny)

ui <- navbarPage("Navbar", 
                 theme = shinytheme("flatly"),
                 navbarMenu(title = "Dropdown menu",
                            tabPanel(title = "Item 1"),
                            tabPanel(title = "Item 2"),
                            tabPanel(title = a("Item 3", href = "https://google.com")),
                            tabPanel(title = HTML("<a href='https://google.com'>Item 4</a>")),
                            tabPanel(title = HTML("Item 5")),
                            tabPanel(title = "Item 6")
                 )
)

server <- function(input, output, session) {}

shinyApp(ui, server)