No mathrm pascals as non latex units, another fallthrough for variable scaler

[alhom]

Re: problem with missing \mathrm{Pa} units in dict - datareducers use \mathrm{Pa} for pressure units (while there is a latexunits separately). Homogenized this to match other reducres, and added a fallthrough for variable scaler so it will still scale if needed (will complain though).