gh-91447: Fix findtext to only give an empty string on None (GH-91486)

The API documentation for [findtext](https://docs.python.org/3/library/xml.etree.elementtree.htmlGH-xml.etree.ElementTree.Element.findtext) states that this function gives back an empty string on "no text content." With the previous implementation, this would give back a empty string even on text content values such as 0 or False. This patch attempts to resolve that by only giving back an empty string if the text attribute is set to `None`. Resolves GH-91447.

Automerge-Triggered-By: GH:gvanrossum
(cherry picked from commit a95e60db748ec6f2c19b5710c11f62e1e4d669f4)

Co-authored-by: Eugene Triguba <eugenetriguba@gmail.com>