Could use a better error message when user requests a bad featureSubset

[bpolacco]

Hello!

Came across this small issue today while running the following code:

dpout.highQuality <- MSstats::dataProcess(frag.mss,
                                          MBimpute = FALSE,
                                          featureSubset = "hiqhQuality",  # <== typo hidden here; q vs g
                                          remove_uninformative_feature_outlier = TRUE)

Error message is:
Error in getOption("MSstatsLog")("INFO", msg) : object 'msg' not found

It was rather puzzling, and made me think a recent MSstats update had broken something. But notice the typo I made for featureSubset. It looks like when an unexpected value is given for featureSubset, the code tries to write a log message that is not yet initialized. I'm guessing the issue is in MSstatsSelectFeatures , where a fall back else {stop ("Unexpected featureSubset value, allowed values are highQuality, ...")}, would be an easy improvement and would have let me find my error much faster.

Thanks!