[LyX/master] Disable branches insert menu if read only

[Scott Kostyshak]

commit 48436186558b8a8610a3ba88468d05799d0df01c
Author: Scott Kostyshak <skost...@lyx.org>
Date:   Wed Feb 19 16:58:31 2014 -0500

    Disable branches insert menu if read only

diff --git a/src/frontends/qt4/Menus.cpp b/src/frontends/qt4/Menus.cpp
index eaf9f24..5a901d8 100644
--- a/src/frontends/qt4/Menus.cpp
+++ b/src/frontends/qt4/Menus.cpp
@@ -1392,7 +1392,7 @@ void MenuDefinition::expandToolbars()
 
 void MenuDefinition::expandBranches(Buffer const * buf)
 {
-       if (!buf)
+       if (!buf || buf->isReadonly())
                return;
 
        BufferParams const & master_params = buf->masterBuffer()->params();