data_frame() returns a data.frame

[jennybc]

This is a minor issue but I discovered it in testing something else. If you use data_frame() to make a zero row, zero column tbl_df … instead, you get a data.frame back.

> class(data_frame(a = 1:5, b = a * 2))
[1] "tbl_df"     "tbl"        "data.frame"

> class(data_frame())
[1] "data.frame"