[LyX/master] Allow new buffer params to be reset to empty

[Juergen Spitzmueller]

commit 5b0de8c373037277bb6454b8b399c983e3fb95df
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Sat Jan 14 09:59:33 2017 +0100

    Allow new buffer params to be reset to empty
---
 src/Buffer.cpp |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 09b7b4a..517cd12 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -912,6 +912,9 @@ int Buffer::readHeader(Lexer & lex)
        params().output_sync_macro.erase();
        params().setLocalLayout(docstring(), false);
        params().setLocalLayout(docstring(), true);
+       params().biblio_opts.erase();
+       params().biblatex_bibstyle.erase();
+       params().biblatex_citestyle.erase();
 
        for (int i = 0; i < 4; ++i) {
                params().user_defined_bullet(i) = ITEMIZE_DEFAULTS[i];