Python3.5: Fix, explicit frame closes could corrupt data
Python3.5: Fix, explicit frame closes could corrupt data

* Unclear why the assertion never triggered so far, but during
  recent "goto coroutines" work it did, so this better gets done
  right.

kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka