patch 9.1.1018: v9.1.0743 causes regression with diff mode

Problem:  v9.1.0743 causes regression with diff mode
Solution: Fix the regression with overlapping regions

closes: #16454

Signed-off-by: Yukihiro Nakadaira <yukihiro.nakadaira@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index 1c7233e..8939bb8 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ