ggplot2 doesn't know how to automatically pick scale for <ts> object

I'm learning about time series object, ts. I used datasets::AirPassenger as the ts object.
To plot the time series with ggplot2, I do one of the following:
(1) Coerce the ts object to a tibble using tk_tbl() in the timetk package.
(2) Coerce the ts to a tibble with as_tibble() and extract the time component using as.yearmon() in the zoo package.
(3) Coerce the ts to a tibble with as_tibble() and extract the time component using date_decimal() in the lubridate package.
All the three methods produce correctly the time series plot. But for methods (2) and (3), I received the message " Don't know how to automatically pick scale for object of type . Defaulting to continuous."

How do I avoid the message from R? I was obviously using a tibble and not a ts. Secondly the output from method (1) and (2) produced similar tibbles but method (1) did not elicit the message while (2) did.
Am I missing something in my understanding of the ts object?

Here are my code:
library(tidyverse)

passengers_tb <- timetk::tk_tbl(AirPassengers, rename_index = "date")

passengers_tb1 <- as_tibble(AirPassengers) |>
rename(value = x) |>
add_column(date = zoo::as.yearmon(time(AirPassengers)), .before = "value")

passengers_tb2 <- as_tibble(AirPassengers) |>
rename(value = x) |>
add_column(date = lubridate::date_decimal(as.numeric(time(AirPassengers))), .before = "value")

ggplot(passengers_tb, aes(x = date, y = value)) +
geom_line() +
labs(title = "(1) Monthly Air Passengers (1949-1960)", x = "Year", y = "Passengers") +
theme_minimal()

ggplot(passengers_tb1, aes(x = date, y = value)) +
geom_line() +
labs(title = "(2) Monthly Air Passengers (1949-1960)", x = "Year", y = "Passengers") +
theme_minimal()

ggplot(passengers_tb2, aes(x = date, y = value)) +
geom_line() +
labs(title = "(3) Monthly Air Passengers (1949-1960)", x = "Year", y = "Passengers") +
theme_minimal()

If you look at str(passengers_tb1) you'll see that the value column is a time series object. A simple way to avoid the (harmless?) error message is to change y = value to y = as.numeric(value).

Yes, ithe harmless error message disappears once I coerce variable value to as.numeric(value). Thanks a lot for your help. It clears my doubt over the problem. Thanks again.