vim-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.
05b2761548

src/nvim/testdir/test_visual.vim

@@ -1280,6 +1280,16 @@ func Test_visual_block_insert_round_off()
   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
+
 " this was leaving the end of the Visual area beyond the end of a line
 func Test_visual_ex_copy_line()
   new