Fix critical error for QT6.
Critical - Out of bounds access in expression 'm_defaultPassword[i]' because 'm_defaultPassword' is empty and 'i' may be non-zero. (CWE-398) in smb/smbauthenticator.cpp:47
From QT6 code:
inline QChar &QString::operator[](qsizetype i) { Q_ASSERT(i >= 0 && i < size()); return data()\[i\]; }
Edited by Alexander Kuznetsov