separate_rows() has error when column is a factor

[al-obrien]

When separating rows with a column in factor format, the following error occurs: Error in nchar(u, itype) : 'nchar()' requires a character vector

This occurred when transitioning to the 1.1.2 version of tidyr using separate_rows(); a similar issue was resolved in the prior version (1.1.1): #1014

Works fine:

df <- tibble(
  x = 1:3,
  y = c("a", "d,e,f", "g,h"),
  z = c("1", "2,3,4", "5,6")
)
separate_rows(df, y, z, convert = TRUE)

Has error: Error in nchar(u, itype) : 'nchar()' requires a character vector

df <- tibble(
  x = 1:3,
  y = factor("a", "d,e,f", "g,h"),
  z = c("1", "2,3,4", "5,6")
)
separate_rows(df, y, z, convert = TRUE)