[LyX/master] We need the "none" return value of main_font_encoding

[Juergen Spitzmueller]

commit 72cebc2514f1e8488a857ace2d2c059bb4e04506
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Mon Apr 23 16:20:36 2018 +0200

    We need the "none" return value of main_font_encoding
---
 src/BufferParams.cpp |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/src/BufferParams.cpp b/src/BufferParams.cpp
index 8143556..7211f12 100644
--- a/src/BufferParams.cpp
+++ b/src/BufferParams.cpp
@@ -3114,7 +3114,12 @@ string const BufferParams::dvips_options() const
 
 string const BufferParams::main_font_encoding() const
 {
-       return font_encodings().empty() ? "default" : font_encodings().back();
+       if (font_encodings().empty()) {
+               if (ascii_lowercase(language->fontenc(*this)) == "none")
+                       return "none";
+               return "default";
+       }
+       return font_encodings().back();
 }