[R-pkg-devel] Error in CHECK caused by dev.off()

Dear all,

I have two variables, foo and bar. The first is TRUE if a png should be

created and the second is TRUE if an already existing one should be 
overwritten.
At the end of the plot I had
if (foo | (foo & bar)) dev.off()
This worked as expected in all versions of my package built in R up to 
v3.6.3. However, when I CHECK the package in v4.0.2 I get:

grDevices::dev.off()

Error in grDevices::dev.off() :
? cannot shut down device 1 (the null device)
Execution halted

I tried:
if (foo | (foo & bar)) {
? dev <- dev.list()
? if (!is.null(dev)) {
??? if (dev == 2) invisible(dev.off())
? }
}
without success (same error).

Even the more general
if (foo | (foo & bar)) {
? graphics.off()
}
did not work.

The plot is called only in an example of one man-page -- though
embedded 
in \donttest{}.
Even if I set both foo and bar to FALSE (i.e., the respective part of 
the code should not be executed at all), I get the same error.

Any ideas/suggestions?

Regards,
Helmut