Fix potential error. (#4650)

### What problem does this PR solve?
#4622

### Type of change

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

rag/nlp/search.py

@@ -465,7 +465,7 @@ class Dealer:
         if not aggs:
             return False
         cnt = np.sum([c for _, c in aggs])
-        tag_fea = sorted([(a, round(0.1*(c + 1) / (cnt + S) / (all_tags.get(a, 0.0001)))) for a, c in aggs],
+        tag_fea = sorted([(a, round(0.1*(c + 1) / (cnt + S) / max(1e-6, all_tags.get(a, 0.0001)))) for a, c in aggs],
                          key=lambda x: x[1] * -1)[:topn_tags]
         doc[TAG_FLD] = {a: c for a, c in tag_fea if c > 0}
         return True
@@ -481,6 +481,6 @@ class Dealer:
         if not aggs:
             return {}
         cnt = np.sum([c for _, c in aggs])
-        tag_fea = sorted([(a, round(0.1*(c + 1) / (cnt + S) / (all_tags.get(a, 0.0001)))) for a, c in aggs],
+        tag_fea = sorted([(a, round(0.1*(c + 1) / (cnt + S) / max(1e-6, all_tags.get(a, 0.0001)))) for a, c in aggs],
                          key=lambda x: x[1] * -1)[:topn_tags]
         return {a: max(1, c) for a, c in tag_fea}