Fix: The Context Generator(Transformer) node can only be followed by a Tokenizer(Indexer) and a Context Generator(Transformer). #9869 (#10515)

### What problem does this PR solve?

Fix: The Context Generator node can only be followed by a Tokenizer and
a Context Generator. #9869
### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/data-flow/constant.tsx

@@ -299,7 +299,9 @@ export const initialHierarchicalMergerValues = {
 export const initialExtractorValues = {
   ...initialLlmBaseValues,
   field_name: ContextGeneratorFieldName.Summary,
-  outputs: {},
+  outputs: {
+    chunks: { type: 'Array<Object>', value: [] },
+  },
 };
 
 export const CategorizeAnchorPointPositions = [