Don't crash with pie menus with more than 8 items.

This will print a warning and users will get overlap of pie buttons, but
it should be quick paper over the cracks and at least should keep
blender working until a more complete fix is coded.

source/blender/editors/interface/interface_layout.c

@@ -2147,7 +2147,11 @@ static void ui_litem_layout_column(uiLayout *litem)
 static RadialDirection ui_get_radialbut_vec(float vec[2], short itemnum)
 {
 	RadialDirection dir;
-	BLI_assert(itemnum < 8);
+
+	if (itemnum < 8) {
+		itemnum %= 8;
+		printf("Warning: Pie menus with more than 8 items are currently unsupported\n");
+	}
 
 	dir = ui_radial_dir_order[itemnum];
 	ui_but_pie_dir(dir, vec);