patch 9.0.0293: messages window not hidden when starting a command line

Problem:    Messages window not hidden when starting a command line.
Solution:   Hide the messages window. (closes #10996)

src/ex_getln.c

@@ -1603,6 +1603,9 @@ getcmdline_int(
 	made_cmdheight_nonzero = TRUE;
 	lastwin->w_p_so = 0;
 	set_option_value((char_u *)"ch", 1L, NULL, 0);
+#ifdef HAS_MESSAGE_WINDOW
+	popup_hide_message_win();
+#endif
 	update_screen(UPD_VALID);                 // redraw the screen NOW
 	made_cmdheight_nonzero = FALSE;
 	lastwin->w_p_so = save_so;