Fix normalized DEM writing in point2dem.
Fix normalized DEM writing in point2dem.

This was accidentally broken when I added support for '--nodata'
option and when I included the nodata value in the output.

ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,njwilson23/StereoPipeline,ScottMcMichael/StereoPipeline,ScottMcMichael/StereoPipeline,oleg-alexandrov/StereoPipeline,ScottMcMichael/StereoPipeline,aaronknister/StereoPipeline,DougFirErickson/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,njwilson23/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,aaronknister/StereoPipeline,NeoGeographyToolkit/StereoPipeline,njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,aaronknister/StereoPipeline,DougFirErickson/StereoPipeline,NeoGeographyToolkit/StereoPipeline,njwilson23/StereoPipeline,ScottMcMichael/StereoPipeline,ScottMcMichael/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline