Add text to combo box: add a new item if text is not found in
        combo box items.

def add_text(self, text):
        """Add text to combo box: add a new item if text is not found in
        combo box items."""
        index = self.findText(text)
        while index != -1:
            self.removeItem(index)
            index = self.findText(text)
        self.insertItem(0, text)
        index = self.findText('')
        if index != -1:
            self.removeItem(index)
            self.insertItem(0, '')
            if text != '':
                self.setCurrentIndex(1)
            else:
                self.setCurrentIndex(0)
        else:
            self.setCurrentIndex(0)