Fix divided by zero issue. (#4784)

### What problem does this PR solve?

#4779

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

rag/nlp/__init__.py

@@ -69,6 +69,7 @@ def find_codec(blob):
 
     return "utf-8"
 
+
 QUESTION_PATTERN = [
     r"第([零一二三四五六七八九十百0-9]+)问",
     r"第([零一二三四五六七八九十百0-9]+)条",
@@ -83,6 +84,7 @@ QUESTION_PATTERN = [
     r"QUESTION ([0-9]+)",
 ]
 
+
 def has_qbullet(reg, box, last_box, last_index, last_bull, bull_x0_list):
     section, last_section = box['text'], last_box['text']
     q_reg = r'(\w|\W)*?(?:？|\?|\n|$)+'
@@ -125,6 +127,7 @@ def has_qbullet(reg, box, last_box, last_index, last_bull, bull_x0_list):
             return has_bull, index
     return None, last_index
 
+
 def index_int(index_str):
     res = -1
     try:
@@ -142,6 +145,7 @@ def index_int(index_str):
                     return -1
     return res
 
+
 def qbullets_category(sections):
     global QUESTION_PATTERN
     hits = [0] * len(QUESTION_PATTERN)
@@ -230,7 +234,10 @@ def is_english(texts):
         return True
     return False
 
+
 def is_chinese(text):
+    if not text:
+        return False
     chinese = 0
     for ch in text:
         if '\u4e00' <= ch <= '\u9fff':
@@ -239,6 +246,7 @@ def is_chinese(text):
         return True
     return False
 
+
 def tokenize(d, t, eng):
     d["content_with_weight"] = t
     t = re.sub(r"</?(table|td|caption|tr|th)( [^<>]{0,12})?>", " ", t)
@@ -416,7 +424,6 @@ def hierarchical_merge(bull, sections, depth):
     bullets_size = len(BULLET_PATTERN[bull])
     levels = [[] for _ in range(bullets_size + 2)]
 
-
     for i, (txt, layout) in enumerate(sections):
         for j, p in enumerate(BULLET_PATTERN[bull]):
             if re.match(p, txt.strip()):
@@ -594,4 +601,3 @@ def naive_merge_docx(sections, chunk_token_num=128, delimiter="\n。；！？"):
         add_chunk(sec, image, '')
 
     return cks, images
-