support getitem when index is a all-false bool tensor

[FlyingQianMM]

PR types

Bug fixes

PR changes

APIs

Describe

When index is a all-false bool tensor, getitem will raise a error as bellow:

import paddle
import numpy as np
data = paddle.to_tensor(np.zeros((2, 4)), dtype='float32')
index = paddle.to_tensor([False, False], dtype='bool')
out = data[index]

After fixed, getitem can run correctly as bellow:

[paddle-bot-old]

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