[LyX/master] Pass two string parameters as reference

[Jean-Marc Lasgouttes]

commit 8dd9cfcf5c24f7f3f15980494ef699f338ed0a00
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Fri Jan 12 16:02:36 2024 +0100

    Pass two string parameters as reference
    
    Spotted by coverity
---
 src/insets/InsetIndex.cpp |    2 +-
 src/insets/InsetIndex.h   |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/insets/InsetIndex.cpp b/src/insets/InsetIndex.cpp
index 67f932e..4227252 100644
--- a/src/insets/InsetIndex.cpp
+++ b/src/insets/InsetIndex.cpp
@@ -292,7 +292,7 @@ void InsetIndex::latex(otexstream & ios, OutputParams const & runparams_in) cons
 
 
 void InsetIndex::processLatexSorting(otexstream & os, OutputParams const & runparams,
-				docstring const latex, docstring const spart) const
+				docstring const & latex, docstring const & spart) const
 {
 	if (contains(latex, '\\') && !contains(latex, '@')) {
 		// Now we need to validate that all characters in
diff --git a/src/insets/InsetIndex.h b/src/insets/InsetIndex.h
index b3fe271..860281b 100644
--- a/src/insets/InsetIndex.h
+++ b/src/insets/InsetIndex.h
@@ -81,7 +81,7 @@ private:
 	void latex(otexstream &, OutputParams const &) const override;
 	///
 	void processLatexSorting(otexstream &, OutputParams const &,
-				 docstring const, docstring const) const;
+				 docstring const &, docstring const &) const;
 	///
 	bool showInsetDialog(BufferView *) const override;
 	///