[LyX/master] By default, use an argument's menu string as its label string.

[Richard Kimberly Heck]

commit affd6101bddb3afebad05e16f36e771c04b7b8e3
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Mon Mar 15 18:25:39 2021 -0400

    By default, use an argument's menu string as its label string.
    
    If one wants different label strings, then provide those first.
---
 src/insets/InsetLayout.cpp |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/src/insets/InsetLayout.cpp b/src/insets/InsetLayout.cpp
index b6056cd..00e63b8 100644
--- a/src/insets/InsetLayout.cpp
+++ b/src/insets/InsetLayout.cpp
@@ -770,6 +770,8 @@ void InsetLayout::readArgument(Lexer & lex)
 		} else if (tok == "menustring") {
 			lex.next();
 			arg.menustring = lex.getDocString();
+			if (arg.labelstring.empty())
+				arg.labelstring = arg.menustring;
 		} else if (tok == "mandatory") {
 			lex.next();
 			arg.mandatory = lex.getBool();