[LyX/master] Fix #12678.

[Pavel Sanda]

commit 9bbec4a75ab89634b298ced8fb4cd06b402a3fd7
Author: Pavel Sanda <sanda at lyx.org>
Date:   Sun Feb 26 22:30:17 2023 +0100

    Fix #12678.
---
 src/Buffer.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 4d7adc3..f03970b 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -941,6 +941,7 @@ int Buffer::readHeader(Lexer & lex)
 	params().clearRemovedModules();
 	params().clearIncludedChildren();
 	params().pdfoptions().clear();
+	params().document_metadata.clear();
 	params().indiceslist().clear();
 	params().backgroundcolor = lyx::rgbFromHexName("#ffffff");
 	params().isbackgroundcolor = false;