I am not sure if I mentioned this but changing to 0 does not help as I am using N-1 cross validation and in the literature it is not regarded as a 'suitable' method of solving the problem.
I created my own function to solve it which works by creating a dummy vector of the same size, std and mean to then replace NaN with acceptable values. Posting this for anyone who comes across this question in google.
Cheers, walter for a response
:)