Blender Git Loki

Freestyle: Fix for versioning code not working properly with new texture options.

To get the versioning code properly work, the condition should have been:

DNA_struct_elem_find(fd->filesdna, "FreestyleLineStyle", "MTex", "*mtex[18]")

The present commit uses another new structure member instead, to avoid referring
to the magic number 18 in the last string literal.