Plotting with Sugiyama: a minor nuissance

The following works fine:

     g <- make_tree(7,2)
     plot(g, layout=layout.sugiyama(g)$layout)

However, when g happens to be a singleton then an error occurs:
Error in norm_coords(layout, -1, 1, -1, 1) : 'layout' not a matrix

A workaround is not difficult:

    lll <- layout.sugiyama(g)$layout
    if (vcount(g) == 1) dim(lll) <- c(1,2)
    plot(g, layout=lll)


plot(g, layout=matrix(layout.sugiyama(g)$layout, ncol=2) )

I assume this is a (minor) igraph R package issue (?)

To be clear, this problem was also posted in this issue on GitHub. Indeed, it seems that it should be corrected in the R interface.