Update ConfigManagerBase.set()
Update ConfigManagerBase.set()

For some reason if I use the <code>saveState()</code> function of a <code>QMainWindow</code> object comparing the <code>QByteArray</code> with None returns true and prevents the <code>set()</code> function from updating the settings value. So I added an explicit condition for None.
janusnic/pyqtconfig,mfitzp/pyqtconfig,MrLeeh/pyqtconfig