[LyX/master] Fix the partial patch for #9740 (XeTeX with TeX fonts).

[Günter Milde]

commit 36b9645b5de6d463b49098c0c0d644a4c5f22ef8
Author: Günter Milde <mi...@lyx.org>
Date:   Sun Oct 25 11:20:43 2015 +0100

    Fix the partial patch for #9740 (XeTeX with TeX fonts).

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 829616a..73d2007 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -1588,7 +1588,7 @@ bool Buffer::makeLaTeXFile(FileName const & fname,
 
        // XeTeX with TeX fonts is only safe with ASCII encoding,
        // See #9740 and FIXME in BufferParams::encoding()
-       if (params().useNonTeXFonts && (runparams.flavor == 
OutputParams::XETEX))
+       if (!params().useNonTeXFonts && (runparams.flavor == 
OutputParams::XETEX))
                runparams.encoding = encodings.fromLyXName("ascii");
 
        string const encoding = runparams.encoding->iconvName();