Don't build GUI Editor when not building the GUI library.

code/nel/tools/3d/object_viewer_qt/src/plugins/CMakeLists.txt

@@ -6,7 +6,11 @@ ADD_SUBDIRECTORY(log)
 ADD_SUBDIRECTORY(disp_sheet_id)
 ADD_SUBDIRECTORY(object_viewer)
 ADD_SUBDIRECTORY(georges_editor)
+
+IF(WITH_GUI)
 ADD_SUBDIRECTORY(gui_editor)
+ENDIF(WITH_GUI)
+
 ADD_SUBDIRECTORY(translation_manager)
 ADD_SUBDIRECTORY(bnp_manager)
 # Note: Temporarily disabled until development continues.