[V1] Change return type on get_multimodal_embeddings() (#19446)

Signed-off-by: Russell Bryant <rbryant@redhat.com>

vllm/model_executor/models/qwen2_5_vl.py

@@ -1016,13 +1016,13 @@ class Qwen2_5_VLForConditionalGeneration(nn.Module, SupportsMultiModal,
     def get_language_model(self) -> torch.nn.Module:
         return self.language_model
 
-    def get_multimodal_embeddings(
-            self, **kwargs: object) -> Optional[MultiModalEmbeddings]:
+    def get_multimodal_embeddings(self,
+                                  **kwargs: object) -> MultiModalEmbeddings:
 
         mm_input_by_modality = self._parse_and_validate_multimodal_inputs(
             **kwargs)
         if not mm_input_by_modality:
-            return None
+            return []
 
         # The result multimodal_embeddings is tuple of tensors, with each
         # tensor correspoending to a multimodal data item (image or video).