patch 9.1.0631: wrong completion list displayed with non-existing dir + fuzzy completion

Problem:  wrong completion list displayed with non-existing dir + fuzzy
          completion (kawarimidoll)
Solution: clear list of matches, if leader did not use fuzzy match
          (glepnir)

fixes: #15357
closes: #15365

Signed-off-by: glepnir <glephunter@gmail.com>
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index 4c2fb45..38324c1 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -1493,6 +1493,11 @@
   call TermWait(buf, 50)
   call VerifyScreenDump(buf, 'Test_pum_highlights_11', {})
 
+  " issue #15357
+  call term_sendkeys(buf, "\<ESC>S/non_exit_folder\<C-X>\<C-F>")
+  call TermWait(buf, 50)
+  call VerifyScreenDump(buf, 'Test_pum_highlights_15', {})
+
   call term_sendkeys(buf, "\<C-E>\<Esc>")
   call TermWait(buf)