Fix: float transfer exception. (#6197)

### What problem does this PR solve?

#6177

### Type of change

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

rag/utils/__init__.py

@@ -19,6 +19,7 @@ import re
 import tiktoken
 from api.utils.file_utils import get_project_base_directory
 
+
 def singleton(cls, *args, **kw):
     instances = {}
 
@@ -89,3 +90,12 @@ def num_tokens_from_string(string: str) -> int:
 def truncate(string: str, max_len: int) -> str:
     """Returns truncated text if the length of text exceed max_len."""
     return encoder.decode(encoder.encode(string)[:max_len])
+
+
+def get_float(v: str | None):
+    if v is None:
+        return float('-inf')
+    try:
+        return float(v)
+    except Exception:
+        return float('-inf')