Fix build failing due to ambigous overload
Fixes the following:
/messagetextedit.cpp:183:46: error: use of overloaded operator '+' is ambiguous (with operand types 'QChar' and 'QChar') cursor.insertText(QString(formatChar + formatChar)); ~~~~~~~~~~ ^ ~~~~~~~~~~ /usr/include/qt/QtCore/qstring.h:1532:22: note: candidate function inline const QString operator+(const QString &s1, QChar s2) ^ /usr/include/qt/QtCore/qstring.h:1534:22: note: candidate function inline const QString operator+(QChar s1, const QString &s2)