Height map Manual Min/Max settings are not stored

Hi!

I've noticed a small bug with the Height map settings:

When you choose Manual Normalization and input values in the Min and Max spinner boxes, if you close and reopen xNormal, values will be reset to 0.0.
Also, if you save settings, those values are not written to the xml file. 

I'm using xNormal v3.18.10.33440

Thanks!

Alex