Bug fix: gettiem by none index

[zyfncg]

PR types

Bug fixes

PR changes

APIs

Describe

Fix a bug of slice by none index in dygraph mode

Example:

# x.shape [2, 2]
y = x[None, None, :, :, None]
y.shape
# expect result:
[1, 1, 2, 2, 1]
# now:
[1, 1, 1, 2, 2]

[hbwx24]

LGTM