patch 8.1.0695: internal error when using :popup

Problem:    Internal error when using :popup.
Solution:   When a menu only exists in Terminal mode give an error. (Naruhiko
            Nishino, closes #3765)
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index 287d59d..663a6a8 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -882,5 +882,18 @@
   delfunc s:act_on_text_changed
 endfunc
 
+func Test_menu_only_exists_in_terminal()
+  if !exists(':tlmenu') || has('gui_running')
+    return
+  endif
+  tlnoremenu  &Edit.&Paste<Tab>"+gP  <C-W>"+
+  aunmenu *
+  try
+    popup Edit
+    call assert_false(1, 'command should have failed')
+  catch
+    call assert_exception('E328:')
+  endtry
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab