Windows: Null pointer dereference in QTextStream.cpp caused by QTextCodec::codecForLocale() returning 0 when running an ICU-build under Cygwin

I get a crash in dumpcpp.exe while building Qt. I might have launched configure with wrong parameters, but that's not the point of the thread.
The crash is in QTextStreamPrivate::flushWriteBuffer(). While doing
codec->fromUnicode(writeBuffer.data(), writeBuffer.size(), &writeConverterState);
codec is actually NULL.
From What i see in my makefiles, Qtextstream.cpp was not build with QT_NO_TEXTCODEC, so code went through
if (!codec)
codec = QTextCodec::codecForLocale();
And from reading QTextCodec::codecForLocale, it is expected that it will return 0 in at least one case. So i think the pointer should be checked again after codecForLocale there, and a less fatal/more verbose error should be raised