core: fix crash in case of NULL message sent to function gui_chat_printf_y_date_tags (closes #1883)

ChangeLog.adoc

@@ -31,6 +31,7 @@ New features::
 
 Bug fixes::
 
+  * core: fix crash in case of NULL message sent to function gui_chat_printf_y_date_tags (issue #1883)
   * core: allow command `/input move_next_word` going to the end of line (issue #1881)
   * core: ignore incomplete ctrl/meta/meta2 codes in keys
   * core: fix display glitch in command errors when a wide char is set in option weechat.look.command_chars (issue #1871)

src/gui/gui-chat.c

@@ -906,6 +906,9 @@ gui_chat_printf_y_date_tags (struct t_gui_buffer *buffer, int y, time_t date,
     time_t date_printed;
     int i, last_y, num_lines_to_add;
 
+    if (!message)
+        return;
+
     if (gui_init_ok && !gui_chat_buffer_valid (buffer, GUI_BUFFER_TYPE_FREE))
         return;