This was broken in da973c3caf (Get rid of CppUnit boilerplate in numeric
validator unit tests, 2021-02-21) which replaced DestroyChildren() in
the old CppUnit test case dtor with just "delete m_text", as this didn't
take care of "text2" created in one of the tests.
Using DestroyChildren() still seems overly side, so ensure that "text2"
is destroyed explicitly.