Bug fix for phenogram when ftype="off"

In developing an exercise recently, I discovered a small bug that was introduced into the function phenogram when I changed (in the latest phytools) version the optional argument spread.labels to default from FALSE to TRUE. This bug causes the function to crash if labels are turned off using ftype="off" under the default conditions.

Here's how it manifests using simulated tree & data:

library(phytools)
packageVersion("phytools")

## [1] '0.4.56'

tree<-pbtree(n=26,tip.label=LETTERS)
x<-fastBM(tree)
phenogram(tree,x) ## works

phenogram(tree,x,ftype="off") ## doesn't work

## Error in optim(zz, ff, yy = yy, mo = mo, ms = ms, cost = cost, method = "L-BFGS-B", : L-BFGS-B needs finite values of 'fn'

phenogram(tree,x,ftype="off",spread.labels=FALSE) ## works

The fix is pretty easy - I just check if ftype="off" and set spread.labels=FALSE if it is. I will put this in the next version of phytools. Here's how it works:

source("http://www.phytools.org/phenogram/v1.4/phenogram.R")
phenogram(tree,x)

phenogram(tree,x,ftype="off") ## now works

OK, that's it for now.