subplot crashes if add_annotation lacks x and y arguments

If I create subplots that use add_annotation and don't pass in values for x and y, subplot crashes RStudio.

Using the example from https://plotly-r.com/bars-histograms.html#multiple-numeric-distributions, the original code works fine. The version below comments out x and y and causes RStudio to crash.

## DO NOT RUN

one_plot <- function(d) {
  plot_ly(d, x = ~price) %>%
    add_histogram() %>%
    add_annotations(
      ~unique(clarity), # x = 0.5, y = 1, 
      xref = "paper", yref = "paper", showarrow = FALSE
    )
}

diamonds %>%
  split(.$clarity) %>%
  lapply(one_plot) %>% 
  subplot(nrows = 2, shareX = TRUE, titleX = FALSE) %>%
  hide_legend()

Start with the supplied R reproducible example from the plotly-r.com bars and histograms page, focusing on add_annotations() with x and y omitted and the surrounding subplot() call. Trace how these entry points handle missing annotation coordinates. Done means the example no longer crashes RStudio when x and y are absent.