[LyX/master] Set buffer when creating a MathData from parts of another one

[Jean-Marc Lasgouttes]

commit ed2f3cb9cfa1e871d48a92d41791a77bd218ab67
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Thu Apr 25 17:13:15 2024 +0200

    Set buffer when creating a MathData from parts of another one
    
    This is triggered by selecting part of an equation under Xcb platform
    (x11). Indeed, the current selection has to be sent to the X11 server
    and BufferView::requestSelection() is called. Eventually
    cap::grabSelection() is the function that creates this partial
    MathData object.
    
    Fixes ticket #12947.
---
 src/mathed/MathData.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/mathed/MathData.cpp b/src/mathed/MathData.cpp
index 5f62d86846..73c1d9db90 100644
--- a/src/mathed/MathData.cpp
+++ b/src/mathed/MathData.cpp
@@ -49,7 +49,9 @@ namespace lyx {
 
 MathData::MathData(Buffer * buf, const_iterator from, const_iterator to)
 	: base_type(from, to), buffer_(buf)
-{}
+{
+	setContentsBuffer();
+}
 
 
 void MathData::setContentsBuffer()