[LyX/master] fix glitch in index reversion

[Juergen Spitzmueller]

commit 1b42d800a3c2d000d4770ba5f2adbf79fc01e0c7
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Sat Jan 28 17:06:35 2023 +0100

    fix glitch in index reversion
---
 lib/lyx2lyx/lyx_2_4.py |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/lyx2lyx/lyx_2_4.py b/lib/lyx2lyx/lyx_2_4.py
index a060962..87cbba2 100644
--- a/lib/lyx2lyx/lyx_2_4.py
+++ b/lib/lyx2lyx/lyx_2_4.py
@@ -4504,9 +4504,15 @@ def revert_index_macros(document):
                                 # construct the latex sequence
                                 icont = xicont + put_cmd_in_ert("@") + xxicont[1:]
                 if len(subentry) > 0:
-                    subentry2 = icont[1:]
+                    if (icont[0] == "\\begin_layout Plain Layout"):
+                        subentry2 = icont[1:]
+                    else:
+                    	subentry2 = icont
                 else:
-                    subentry = icont[1:]
+                    if (icont[0] == "\\begin_layout Plain Layout"):
+                        subentry = icont[1:]
+                    else:
+                    	subentry = icont
             elif imacro == "sortkey":
                 sortkey = icont
             # Everything stored. Delete subinset.