[LyX/master] Extend workaround for polyglossia in Russian Math.lyx

[Juergen Spitzmueller]

commit e6f7654a30f228da19c60102ea81158d8427b22b
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Sun Jun 21 12:16:16 2026 +0200

    Extend workaround for polyglossia in Russian Math.lyx
---
 lib/doc/ru/Math.lyx | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/doc/ru/Math.lyx b/lib/doc/ru/Math.lyx
index 2523376747..dca32349bb 100644
--- a/lib/doc/ru/Math.lyx
+++ b/lib/doc/ru/Math.lyx
@@ -155,6 +155,7 @@
   \file_input:n { t2aenc.dfu }
   \group_end:
   \ExplSyntaxOff
+  \providecommand*\cyr{}
 \fi
 \@ifpackageloaded{fontspec}{
   % latinmodern (used with non-TeX fonts) does not have a combining cedilla