mxRun printing empty arrays during run?

starting in 821 (or perhaps 820), running a model causes a series of empty arrays to be printed early on in the execution...

> fit = mxRun(model)
Running ACE
[[1]]
[1] NA

[[2]]
[1] NA

[[3]]
[1] NA

[[4]]
[1] NA

[[5]]
[1] NA

[[6]]
[1] NA

[[1]]
[1] NA

[[2]]
[1] NA

[[3]]
[1] NA

[[4]]
[1] NA

[[5]]
[1] NA

[[6]]
[1] NA