Check for truthy `rope_parameters` not the existence of it (#30983)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
(cherry picked from commit 19c58339)

vllm/transformers_utils/config.py

@@ -318,15 +318,15 @@ def patch_rope_parameters(config: PretrainedConfig) -> None:
         # Transformers v4 installed, legacy config fields may be present
         if (rope_scaling := getattr(config, "rope_scaling", None)) is not None:
             config.rope_parameters = rope_scaling
-        if rope_theta is not None:
-            if not hasattr(config, "rope_parameters"):
+        if (
+            rope_theta is not None or partial_rotary_factor is not None
+        ) and not getattr(config, "rope_parameters", None):
             config.rope_parameters = {"rope_type": "default"}
+        if rope_theta is not None:
             config.rope_parameters["rope_theta"] = rope_theta
         if partial_rotary_factor is not None:
-            if not hasattr(config, "rope_parameters"):
-                config.rope_parameters = {"rope_type": "default"}
             config.rope_parameters["partial_rotary_factor"] = partial_rotary_factor
-    elif rope_theta is not None or hasattr(config, "rope_parameters"):
+    elif rope_theta is not None or getattr(config, "rope_parameters", None):
         # Transformers v5 installed
         # Patch these fields in case they used non-standard names
         if rope_theta is not None: