Extracting standard errors from random effects of class GAMM in r

I have built a generalized additive mixed effects model with a fixed effect and a random intercept effect (that is a categorical variable). After running the model I am able to extract the random intercepts per each of my categories using ranef(m1$lme)$x[[1]]. However, when I try to extract the standard errors of the random effects using se.ranef(m1$lme), the function does not work. Other attempts using se.ranef(m1) and se.ranef(m1$gam) dont work either. I don't know if this is because these function only apply to models of the class lmer?

Can any one help me so that I can pull out my standard errors of my random intercept from a class "gamm"? I would like to use the random intercepts and standard errors to plot the Best Linear Unbiased Predictors of my gamm model.

My initial model is of the form: gamm(y ~ s(z), random=list(x=~1), data=dat).