patch 8.1.0213: CTRL-W CR does not work properly in a quickfix window

Problem:    CTRL-W CR does not work properly in a quickfix window.
Solution:   Split the window if needed. (Jason Franklin)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index c8f0984..d41815f 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -3504,3 +3504,21 @@
   call assert_equal([' 1 abc:pat1:  '],
 			\ split(execute('filter /pat1/ clist'), "\n"))
 endfunc
+
+" Tests for the "CTRL-W <CR>" command.
+func Xview_result_split_tests(cchar)
+  call s:setup_commands(a:cchar)
+
+  " Test that "CTRL-W <CR>" in a qf/ll window fails with empty list.
+  call g:Xsetlist([])
+  Xopen
+  let l:win_count = winnr('$')
+  call assert_fails('execute "normal! \<C-W>\<CR>"', 'E42')
+  call assert_equal(l:win_count, winnr('$'))
+  Xclose
+endfunc
+
+func Test_view_result_split()
+  call Xview_result_split_tests('c')
+  call Xview_result_split_tests('l')
+endfunc