genRxControl is NULL for pkncaControl()

[billdenney]

@mattfidler, When I'm using pkncaControl(), the genRxControl item is not present. That causes an error at this line:

https://github.com/nlmixr2/nlmixr2est/blob/7204214a9aaa324ad5ac04055d88fda2ea49f02e/R/nlmixr2.R#L253

Should I set it to FALSE within pkncaControl() or does it make more sense to modify that line to check for NULL? Maybe make that line into isTRUE(.ctl$genRxControl)?

[billdenney]

I'm not sure why it works some times and not others. It may be package load order.

[mattfidler]

Its seeing if it can adjust parameters. Sometimes it can sometimes it cant. I suppose isTRUE makes more sense