BUG: reset_index may return wrong results when the target df is not executed

[ChengjieLi28]

Note that the issue tracker is NOT the place for general support. For
discussions about development, questions about usage, or any general questions,
contact us on https://discuss.xorbits.io/.
Reproduce:

import xorbits.pandas as pd

df = pd.DataFrame({'a': [i for i in range(500)], "b": [i * 2 for i in range(500)]}, chunk_size=10)
def t(x):
    return len(x[x % 3 == 0])

res = df.groupby("a", as_index=False)["b"].agg([t])
# correct result if print(res) here
# print(res)
res = res.reset_index(drop=True)
print(res)