Fix too long query exception. (#4729)

### What problem does this PR solve?


### Type of change

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

rag/nlp/query.py

@@ -185,7 +185,7 @@ class FulltextQueryer:
                     for s in syns
                 ]
             )
-            if syns:
+            if syns and tms:
                 tms = f"({tms})^5 OR ({syns})^0.7"
 
             qs.append(tms)