patch 8.1.2314: vi' sometimes does not select anything

Problem:    vi' sometimes does not select anything.
Solution:   Recognize an empty selection. (Christian Brabandt, closes #5183)

src/testdir/test_textobjects.vim

@@ -47,6 +47,9 @@ func Test_quote_selection_selection_exclusive()
   set selection=exclusive
   exe "norm! fdvhi'y"
   call assert_equal('bcde', @")
+  let @"='dummy'
+  exe "norm! $gevi'y"
+  call assert_equal('bcde', @")
   set selection&vim
   bw!
 endfunc