修改bug，识别三级标题

ppt_api.py

@@ -222,6 +222,11 @@ def catalogue_extract(structure):
 
     catalogue_list = []
     for level, text in structure[:-1]:
+        text = str(text).strip(" ").strip("\n")
+        erji_p = re.findall(pantten_erjibiaoti, text)
+        yiji_p = re.findall(pantten_yijibiaoti, text)
+        if erji_p == [] and yiji_p == []:
+            continue
         catalogue_list.append(str(text).strip(" ").strip("\n"))
     catalogue_str = "\n".join(catalogue_list)
     return catalogue_list, catalogue_str