当topic包含特殊字符时，xmind_content_dict读取为空，很多属性读取不到 #22
Description
WARNING:root:This is a blank sheet(None), should have at least 1 sub topic(test suite)
xmind_content_dict=[{'id': '76255e848420dcc93656efda15', 'title': None, 'topic': {'id': '76255e848420d91fe98c4526dd', 'link': None, 'title': None, 'note': None, 'label': None, 'comment': None, 'markers': []}}]