plot_spectra() throws error when detect.outliers = F and no alternative title is given

[jmh579]

An error is thrown when the code below is run, but it should work without a title.

library(tidyverse)
library(waves)
ikeogu.2017 %>% 
  dplyr::select(sample.id, starts_with("X")) %>% 
  plot_spectra(detect.outliers = FALSE)

Error in plot_spectra(., detect.outliers = FALSE) : 
  object 'plot.title' not found

When the parameter alternative.title is supplied (even with empty quotes), this error does not appear:

library(tidyverse)
library(waves)
ikeogu.2017 %>% 
  dplyr::select(sample.id, starts_with("X")) %>% 
  plot_spectra(detect.outliers = FALSE, alternative.title = "")