fixing baseTable() function

using `array_pop()` here will get the last element of `$classes` array, meaning 'the furthermost child class' instead of 'the furthermost ancestor class'. So the `isPublished()` function (which relies on `baseTable()`) delivers unpredictable results.

replacing by `array_shift()`, as it's also done in the related `baseTable()` function of `DataObject` class