[LyX/master] Do not allow to split InsetArgument

[Juergen Spitzmueller]

commit 8b506f860bcd11d00a2d1a370ba4e7500324c23f
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Tue Feb 17 09:06:25 2026 +0100

    Do not allow to split InsetArgument
    
    Candidate for 2.5.1
---
 src/insets/InsetArgument.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/insets/InsetArgument.cpp b/src/insets/InsetArgument.cpp
index 0c1afec0b7..8344b2c909 100644
--- a/src/insets/InsetArgument.cpp
+++ b/src/insets/InsetArgument.cpp
@@ -242,6 +242,10 @@ bool InsetArgument::getStatus(Cursor & cur, FuncRequest const & cmd,
 {
 	switch (cmd.action()) {
 
+	case LFUN_INSET_SPLIT:
+		flag.setEnabled(false);
+		return true;
+
 	case LFUN_INSET_MODIFY: {
 		string const first_arg = cmd.getArg(0);
 		if (first_arg == "changetype") {