vim-patch:8.2.0934: lhelpgrep twice in help window doesn't jump to the help topic

Problem:    Running lhelpgrep twice in a help window doesn't jump to the help
            topic.
Solution:   Check whether any window with the location list is present.
            (Yegappan Lakshmanan, closes vim/vim#6215)
ec98e93a82

src/nvim/quickfix.c

@@ -6952,8 +6952,9 @@ void ex_helpgrep(exarg_T *eap)
   if (au_name != NULL) {
     apply_autocmds(EVENT_QUICKFIXCMDPOST, au_name,
                    curbuf->b_fname, true, curbuf);
-    if (!new_qi && IS_LL_STACK(qi) && qf_find_buf(qi) == NULL) {
+    // When adding a location list to an existing location list stack,
-      // autocommands made "qi" invalid
+    // if the autocmd made the stack invalid, then just return.
+    if (!new_qi && IS_LL_STACK(qi) && qf_find_win_with_loclist(qi) == NULL) {
       decr_quickfix_busy();
       return;
     }

src/nvim/testdir/test_quickfix.vim

@@ -4625,6 +4625,24 @@ func Test_cquit()
   call assert_fails('-3cquit', 'E16:')
 endfunc
 
+" Running :lhelpgrep command more than once in a help window, doesn't jump to
+" the help topic
+func Test_lhelpgrep_from_help_window()
+  call mkdir('Xtestdir/doc', 'p')
+  call writefile(['window'], 'Xtestdir/doc/a.txt')
+  call writefile(['buffer'], 'Xtestdir/doc/b.txt')
+  let save_rtp = &rtp
+  let &rtp = 'Xtestdir'
+  lhelpgrep window
+  lhelpgrep buffer
+  call assert_equal('b.txt', fnamemodify(@%, ":p:t"))
+  lhelpgrep window
+  call assert_equal('a.txt', fnamemodify(@%, ":p:t"))
+  let &rtp = save_rtp
+  call delete('Xtestdir', 'rf')
+  new | only!
+endfunc
+
 " Test for adding an invalid entry with the quickfix window open and making
 " sure that the window contents are not changed
 func Test_add_invalid_entry_with_qf_window()