LME Question

I am trying to run a linear mixed effects model on some data I have. My participants are nested within 27 organizations so I have to control for this group. I have  three dependent variables (sales, tips, and employee performance) when I attempt to calculate the null model for these three DVs I get the following error message below:

Null.SALES<-lme(SALES~1,random=~1|GROUP,data=tccbtips)

Error in `rownames<-`(`*tmp*`, value = rownames(Fitted) <- origOrder) :
  attempt to set rownames on object with no dimensions
In addition: Warning message:
In Ops.factor(y[revOrder], Fitted) : - not meaningful for factors