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>

src/message.c

@@ -1747,7 +1747,7 @@ msg_outtrans_len_attr(char_u *msgstr, int len, int attr)
 
     // When drawing over the command line no need to clear it later or remove
     // the mode message.
-    if (msg_row >= cmdline_row && msg_col == 0)
+    if (msg_silent == 0 && len > 0 && msg_row >= cmdline_row && msg_col == 0)
     {
 	clear_cmdline = FALSE;
 	mode_displayed = FALSE;

src/testdir/dumps/Test_mode_cleared_after_silent_message_1.dump

@@ -0,0 +1,10 @@
+>f+0&#ffffff0|o@1|b|a|r| @68
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|-+2#0000000&@1| |V|I|S|U|A|L| |-@1| +0&&@34|1| @8|1|,|1| @10|A|l@1| 

src/testdir/dumps/Test_mode_cleared_after_silent_message_2.dump

@@ -0,0 +1,10 @@
+>o+0&#ffffff0@1|b|a|r| @69
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+| +0#0000000&@56|1|,|1| @10|A|l@1| 

src/testdir/test_messages.vim

@@ -382,6 +382,29 @@ func Test_message_not_cleared_after_mode()
   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

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1155,
 /**/
     1154,
 /**/