Regression: crash if QFileInfo::path() is called for a non-existent drive

Error can be reproduced with Qt4.8.3 compiled with Visual Studio x64 Cross Tools Command Prompt (2010).
With Qt4.8.1 compiled with Visual Studio x64 Cross Tools Command Prompt (2010) the use case works ok.

Use case:

Call a QFileInfo::path() (http://qt-project.org/doc/qt-4.8/qfileinfo.html#pathx) for a non-existant drive, for example:

// note: drive 'e' does not exist
QFileInfo info(QLatin1String("e:test.txt"));
QString szPath=info.path(); 

--> error: crash occurs.

SHA fd2eb070128ab6ef6b5c9343a0921f6b5a0bc041 has modified QFileSystemEntry::path() function on
$QTDIR\src\corelib\io\qfilesystementry.cpp. This has caused the regression.