address greptile review feedback (greploop iteration 1)

- Fix eager asyncio.Lock() allocation in _get_async_refresh_lock by using
  get() + conditional set instead of setdefault (avoids discarded Lock per call)
- Add warning log when pages_processed is None in ocr_cost to surface
  potentially malformed OCR responses instead of silently returning 0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

litellm/cost_calculator.py

@@ -1817,6 +1817,10 @@ def ocr_cost(
 
     pages_processed = response.usage_info.pages_processed
     if pages_processed is None:
+        verbose_logger.warning(
+            "ocr_cost: pages_processed is None for model=%s; returning 0 cost",
+            model,
+        )
         return 0.0, 0.0
 
     ocr_cost_per_page: float = 0.0

litellm/llms/vertex_ai/vertex_llm_base.py

@@ -359,9 +359,11 @@ class VertexBase:
 
     def _get_async_refresh_lock(self, credential_cache_key: tuple) -> asyncio.Lock:
         """Get or create an asyncio.Lock for the given credential cache key."""
-        return self._async_refresh_locks.setdefault(
-            credential_cache_key, asyncio.Lock()
-        )
+        lock = self._async_refresh_locks.get(credential_cache_key)
+        if lock is None:
+            lock = asyncio.Lock()
+            self._async_refresh_locks[credential_cache_key] = lock
+        return lock
 
     def _try_get_cached_token(
         self,