Dealing with NAs

Hi

I am trying to estimate parameter values with mlogit. I attach a part of my data.

My code is

x=mlogit.data(y,choice="voittaja",shape="long",id.var="id",alt.var="numero")

summary(mlogit(voittaja  ~ Ie-1 , data=x, na.action=na.pass))



But i get 



Error in if (abs(x - oldx) < ftol) { : 
  missing value where TRUE/FALSE needed


Because there is Na in D2. 

What should i do to make it work?