changed condition to be less error prone

handler.py

@@ -65,8 +65,10 @@ class WhisperParameterHandler(BaseSettings):
     return_timestamps: Optional[Literal["word", True]] = None
 
     @field_validator("return_timestamps", mode="before")
-    def cannonize_timestamps(cls, value: Any):
-        if value == "True":
+    def cannonize_timestamps(cls, value: Optional[str]):
+        if value is None:
+            return None
+        if value.lower() == "true":
             logging.info("return_timestamps == 'True'")
             return True