patch 9.1.1155: Mode message not cleared after :silent message

Problem:  Mode message not cleared after :silent message
          (after 9.0.1634).
Solution: Don't reset mode_displayed when the message is empty.
          (zeertzjq)

fixes: neovim/neovim#32641
closes: #16744

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_messages.vim b/src/testdir/test_messages.vim
index c566bbc..87b1131 100644
--- a/src/testdir/test_messages.vim
+++ b/src/testdir/test_messages.vim
@@ -382,6 +382,29 @@
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_mode_cleared_after_silent_message()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+    edit XsilentMessageMode.txt
+    call setline(1, 'foobar')
+    autocmd TextChanged * silent update
+  END
+  call writefile(lines, 'XsilentMessageMode', 'D')
+  let buf = RunVimInTerminal('-S XsilentMessageMode', {'rows': 10})
+
+  call term_sendkeys(buf, 'v')
+  call TermWait(buf)
+  call VerifyScreenDump(buf, 'Test_mode_cleared_after_silent_message_1', {})
+
+  call term_sendkeys(buf, 'd')
+  call TermWait(buf)
+  call VerifyScreenDump(buf, 'Test_mode_cleared_after_silent_message_2', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XsilentMessageMode.txt')
+endfunc
+
 " Test verbose message before echo command
 func Test_echo_verbose_system()
   CheckRunVimInTerminal