Fix crash when clicking on "try again".

6895== Invalid read of size 8

6895== at 0x9294220: KPasswordDialog::password() const (kpassworddialog.cpp:201)

6895== by 0x42AFDD: SettingsPasswordRequester::requestManualAuth(bool*) (settingspasswordrequester.cpp:174)

6895== Address 0x2f34cc50 is 48 bytes inside a block of size 56 free'd

6895== at 0x4C2A69D: operator delete(void*) (vg_replace_malloc.c:576)

6895== by 0x929342D: KPasswordDialog::~KPasswordDialog() (kpassworddialog.cpp:80)

6895== by 0xA9C83E2: QDialog::exec() (qdialog.cpp:540)

6895== by 0x42AF7F: SettingsPasswordRequester::requestManualAuth(bool*) (settingspasswordrequester.cpp:172)

CCMAIL: dvratil@kde.org