Even if a object is deleted, its render_pre function could be called.
Especially, Evas Textblock is calling relayout() function if there are
any changes. In relayout() function, it creates at least one paragraph
and one line. Normally, all of paragraphs and its line should be removed
when Evas Textblock object is deleted. But, paragraphs and lines which are
created after deleting its object never be free'd.