Hello I seem to have encountered a error

Hello, I seem to have encountered a error regarding the base GPT Index class. I am generating custom nodes through a for loop. As you can see I am including the doc_id for each node and have checked that all are filled. Yet, I get this error: ValueError: Reference doc id is None. It refers me to this file /site-packages/llama_index/indices/base.py and highlight the following line:

if index_struct is None:
...
--> 108 raise ValueError("Reference doc id is None.")
109 result_tups.append(
110 NodeEmbeddingResult(id, id_to_node_map[id], embed, doc_id=doc_id)

Code
nodes = []
#transcript_array refers to an array of phrases that Whisper outputs.
for index,phrase in enumerate(transcript_array):
#current obj index
node = Node(text=phrase['content'] + " " + str(phrase['start']), doc_id=index)
if index > 0 and index < len(transcript_array) - 1:
node.relationships[DocumentRelationship.PREVIOUS] = index - 1
node.relationships[DocumentRelationship.NEXT] = index + 1
elif index == 0:
node.relationships[DocumentRelationship.NEXT] = index + 1
elif index == len(transcript_array) - 1:
node.relationships[DocumentRelationship.PREVIOUS] = index - 1
nodes.append(node)
index = GPTSimpleVectorIndex(nodes)

Could it be from my custom nodes? I have attached a txt file of how they look like when i print(nodes)I am following the tutorial from here so some help would be really appreciated.https://gpt-index.readthedocs.io/en/latest/guides/primer/usage_pattern.html