Error when ylim passed to addSeries and on=NA

[joshuaulrich]

addSeries() throws an error if adding a new panel (on = NA) an ylim is present. This happens whether called via addSeries() directly or via lines() or points(). May be related to #76.

require(xts)
data(sample_matrix)
x <- as.xts(sample_matrix, dateFormat="Date")
plot(diff(log(x[,4])))
addSeries(diff(log(x[,1])), ylim=c(-1,1)/100)
# Error in diff(x) * c(Env$pad1, Env$pad3) : 
#   non-numeric argument to binary operator
# In addition: Warning message:
# In structure(ylim, fixed = fixed) :
#   Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
#   Consider 'structure(list(), *)' instead.