patch 9.0.0114: the command line takes up space even when not used

Problem:    The command line takes up space even when not used.
Solution:   Allow for 'cmdheight' to be set to zero. (Shougo Matsushita,
            closes #10675, closes #940)
diff --git a/src/getchar.c b/src/getchar.c
index a3de650..f3dbe4a 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -2096,6 +2096,10 @@
     --no_mapping;
     --allow_keys;
 
+    // redraw the screen after getchar()
+    if (p_ch == 0)
+	update_screen(CLEAR);
+
     set_vim_var_nr(VV_MOUSE_WIN, 0);
     set_vim_var_nr(VV_MOUSE_WINID, 0);
     set_vim_var_nr(VV_MOUSE_LNUM, 0);