Handle searching dataset without embedding model (#16742)

### Summary

Handle searching dataset without embedding model

In this PR, Searching datasets with different embedding models or
searching dataset with/without embedding models are not allowed. We will
improve the behavior later.

test/unit_test/api/apps/services/test_delete_datasets.py

@@ -74,6 +74,7 @@ def _load_delete_datasets_module(monkeypatch, *, f2d_rows, file_filter_delete):
             delete_by_id=lambda kb_id: True,
             query=lambda **kwargs: [],
         ),
+        validate_dataset_embedding_models=lambda kbs: None,
     )
     _stub(
         monkeypatch,