is.layer does not support geom_msa

[jonaudet]

Hi,
Great work on the ggtree and ggtreeExtra packages.
I was trying to combine an msa plot (using ggmsa) with a tree as suggested here, but ran into a "argument 'data' is missing, with no default" error.

I believe the problem can be traced to this line, added more than a year after the above link:
https://github.com/YuLab-SMU/ggtreeExtra/blame/76d6869addc3e99ce1e919c738a3a7074a361277/R/utilities.R#L160

running:

do.call(geom_line, list())

Produces:
geom_line: na.rm = FALSE, orientation = NA stat_identity: na.rm = FALSE position_identity

but running:

do.call(geom_msa, list())

Produces:

Error in (function (data, font = "helvetical", mapping = NULL, color = "Chemistry_AA", : argument "data" is missing, with no default

I thought I would report the problem, but it seems no one else has run into this issue in the 18 months since the change...