patch 9.1.1263: string length wrong in get_last_inserted_save()

Problem:  string length wrong in get_last_inserted_save()
          (after v9.1.1222)
Solution: when removing trailing ESC, also decrease the string length
          (Christ van Willegen)

closes: #16961

Signed-off-by: Christ van Willegen <cvwillegen@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/edit.c b/src/edit.c
index a2a004c..3fa95cd 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -3022,7 +3022,7 @@
 	return NULL;
 
     if (insert.length > 0 && s[insert.length - 1] == ESC)	// remove trailing ESC
-	s[insert.length - 1] = NUL;
+	s[--insert.length] = NUL;
     return s;
 }