display: push the titlebar to the screen as soon as it has been drawn

To avoid an ncurses hiccup (miscoloring) when running on musl.

This fixes https://savannah.gnu.org/bugs/?50787.
Reported-by: Avi Halachmi <avihpit@yahoo.com>

src/winio.c

@@ -2078,6 +2078,7 @@ void titlebar(const char *path)
     wattroff(topwin, interface_color_pair[TITLE_BAR]);
 
     wnoutrefresh(topwin);
+    doupdate();
 }
 
 /* Display a normal message on the statusbar, quietly. */