When I compile libredwg without ```--enable-debug``` (tested on mingw cross compilation). The conversion of DWG with MATERIAL class to JSON and back is not working. Output DWG file is not possible to open in AutoCAD.

This is partially related to the implementation of MATERIAL class. 
Fix MATERIAL class
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : Fix MATERIAL class
Issue date:

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When I compile libredwg without ```--enable-debug``` (tested on mingw cross compilation). The conversion of DWG with MATERIAL class to JSON and back is not working. Output DWG file is not possible to open in AutoCAD.

This is partially related to the implementation of MATERIAL class. 
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