[R-meta] Problems using rma.mh

[David Fisher]

Dear metafor community,

I am a Stata user with only limited knowledge of R.  I am trying to
validate some Stata code by comparing with output from metafor; in
particular, sparse data/zero cells using Mantel-Haenszel methods.

My reference is Wolfgang's page
"http://www.metafor-project.org/doku.php/tips:comp_mh_different_software".
If I type:

library(metafor)
dat <- dat.nielweise2007
rma.mh(measure="OR", ai=ai, n1i=n1i, ci=ci, n2i=n2i, data=dat)

...then I successfully obtain the output shown on the webpage.
However, if I alter the command in (seemingly) any way, I get the
following error:

Error in sprintf(format, names(x)) :
  invalid format '%NA'; use format %s for character objects

For instance, if I limit the dataset to studies with zero events in
the treatment arm:

rma.mh(measure="OR", ai=ai, n1i=n1i, ci=ci, n2i=n2i,
data=dat2007[which(dat2007$ai==0),])

...and similarly if I attempt to use another data frame, or import
from Stata using "read.dta".  Furthermore, I do not appear to have the
same issue if I use another model.  For instance, the following runs
with no problem:

rma(measure="OR", ai=ai, n1i=n1i, ci=ci, n2i=n2i,
data=dat2007[which(dat2007$ai==0),])

I am using a fresh install of R 4.0.1 and of the metafor package.

Could someone point me in the right direction?

Many thanks,

David.