no plain formatter

The function number_field_formatter_info() does not define a plain formatter.
But it is called in the file content_views.inc line 287.
This happens, when you have a argument in a view from type integer and the allowed values from this integer are somethink link this:
0|foo
1|bar
2|foobar

This problem can be fixed, if you add the line:
'plain' => array('label' => '9999', 'field types' => array('number_integer', 'number_decimal')),
in the number_field_formatter_info()