patch 8.2.4261: accessing invalid memory in a regular expression

Problem:    Accessing invalid memory when a regular expression checks the
            Visual area while matching in a string.
Solution:   Do not try matching the Visual area in a string.
diff --git a/src/testdir/test_help.vim b/src/testdir/test_help.vim
index 3e358d6..b8b9bbc 100644
--- a/src/testdir/test_help.vim
+++ b/src/testdir/test_help.vim
@@ -1,6 +1,7 @@
 " Tests for :help
 
 source check.vim
+import './vim9.vim' as v9
 
 func Test_help_restore_snapshot()
   help
@@ -168,5 +169,15 @@
   endtry
 endfunc
 
+func Test_help_using_visual_match()
+  let lines =<< trim END
+      call setline(1, ' ')
+      /^
+      exe "normal \<C-V>\<C-V>"
+      h5\%V€]
+  END
+  call v9.CheckScriptFailure(lines, 'E149:')
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab