geom_textpath() always draw a empty box when label is ""

[Hy4m]

Hi, thank you so much for writing such a nice package.
But I noticed that ggplot2::geom_text () is OK when label is empty, but geomtextpath::geom_textpath() always draws a blank box. The following is an example:

library(ggplot2)
  
## draw empty text with geom_text(), it's OK
df <- data.frame(x = 1, y = 1, label = "")
  
  ggplot(df, aes(x, y, label = label)) +
    geom_text()
  
## draw empty text with geom_textpath(), it always draw a empty box 
tt <- seq(0, 2*pi, length.out = 300)
df2 <- data.frame(x = cos(tt), y = sin(tt), label = "")
  ggplot(df2, aes(x, y, label = label)) +
    geomtextpath::geom_textpath()