Revert "Added 'na.rm = T' to mean calculation"
Revert "Added 'na.rm = T' to mean calculation"

This reverts commit a40cfed2d779ac83cd69999e166470a4f89da61c.
Originally added NA handling due to mistakinly assuming they were causing problems. Revert changes because the problem was elsewhere.

luisvalesilva/hwglabr,hochwagenlab/hwglabr