[gcalctool] Remove compile warning

[Robert Ancell <rancell src gnome org>]

commit 3e0e34622681488d97f57ead35079c7edd9757a9
Author: Robert Ancell <robert ancell canonical com>
Date:   Tue Nov 23 14:16:24 2010 +1100

    Remove compile warning

 src/math-buttons.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/math-buttons.c b/src/math-buttons.c
index 3da1e8d..85cd735 100644
--- a/src/math-buttons.c
+++ b/src/math-buttons.c
@@ -853,6 +853,7 @@ load_mode(MathButtons *buttons, ButtonMode mode)
     GError *error = NULL;
 
     switch (mode) {
+    default:
     case BASIC:
         builder_ptr = &buttons->priv->basic_ui;
         builder_file = UI_BASIC_FILE;