patch 8.2.4154: ml_get error when exchanging windows in Visual mode

Problem:    ml_get error when exchanging windows in Visual mode.
Solution:   Correct end of Visual area when entering another buffer.
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index a187aa8..72f5388 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -1318,5 +1318,15 @@
   bwipe!
 endfunc
 
+" this was causing an ml_get error
+func Test_visual_exchange_windows()
+  enew!
+  new
+  call setline(1, ['foo', 'bar'])
+  exe "normal G\<C-V>gg\<C-W>\<C-X>OO\<Esc>"
+  bwipe!
+  bwipe!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab