bug fix - make sure no embedding is required with OpenAI (#10426)

bug fix

llama_index/indices/managed/vectara/base.py

@@ -70,7 +70,9 @@ class VectaraIndex(BaseManagedIndex):
         super().__init__(
             show_progress=show_progress,
             index_struct=index_struct,
-            service_context=ServiceContext.from_defaults(llm=None, llm_predictor=None),
+            service_context=ServiceContext.from_defaults(
+                llm=None, llm_predictor=None, embed_model=None
+            ),
             **kwargs,
         )
         self._vectara_customer_id = vectara_customer_id or os.environ.get(