Bug in lme4: attr(mod@frame, "na.action") is not re-initialized to NULL

I think I found a bug... and it may affect several versions of lmer (but I
did not try the one before 1.0).
The bug is that the attribute na.action of the model frame is not
re-initialized to NULL (both in lmer and glmer).

example:

data <- data.frame(y=rnorm(100), K=factor(rep(1:10,10)))
data[3, "y"] <- NA
library(lme4)
mod <- lmer(y~1+(1|K), data=data)
dim(mod at frame) # 99 2 The model frame has excluded the line as it should
attr(mod at frame, "na.action") # 3 The value 3 is still considered missing
while it should not

This feature is slightly annoying because it creates the function refit to
crash and others using refit (I came to discover that from a crash in
PBmodcomp from pbkrtest)...

example:

refit(mod, simulate(mod)) # CRASH
attr(mod at frame,"na.action") <- NULL # fast and dirty patch...
refit(mod, simulate(mod)) # works

Thanks to the lmer team for your great work!
PS: If you don't see that as a bug, please send an informative warning.

sessionInfo()

R version 3.0.2 (2013-09-25)
Platform: x86_64-pc-linux-gnu (64-bit)

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] pbkrtest_0.3-8 MASS_7.3-29    lme4_1.1-4     Rcpp_0.11.0
Matrix_1.1-2

loaded via a namespace (and not attached):
[1] grid_3.0.2          lattice_0.20-27     minqa_1.2.3
[4] nlme_3.1-113        RcppEigen_0.3.2.0.3 splines_3.0.2
[7] tools_3.0.2