fix: raise instead of return ValueError (#3189)

These couple of cases used to return ValueError; should raise it
instead.

python/python/tests/test_query.py

@@ -30,6 +30,7 @@ from lancedb.query import (
     PhraseQuery,
     Query,
     FullTextSearchQuery,
+    ensure_vector_query,
 )
 from lancedb.rerankers.cross_encoder import CrossEncoderReranker
 from lancedb.table import AsyncTable, LanceTable
@@ -1501,6 +1502,18 @@ def test_search_empty_table(mem_db):
     assert results == []
 
 
+def test_ensure_vector_query_empty_list():
+    """Regression: ensure_vector_query used to return instead of raise ValueError."""
+    with pytest.raises(ValueError, match="non-empty"):
+        ensure_vector_query([])
+
+
+def test_ensure_vector_query_nested_empty_list():
+    """Regression: ensure_vector_query used to return instead of raise ValueError."""
+    with pytest.raises(ValueError, match="non-empty"):
+        ensure_vector_query([[]])
+
+
 def test_fast_search(tmp_path):
     db = lancedb.connect(tmp_path)