MetaTensor size bug in transform function

[chuxiang93]

Since SIZE is a function of the class metatensor, this sentence does not work. The correct way should be "fg_indices.size()[0]".

MONAI/monai/transforms/utils.py

Line 512 in f407fcc

pos_ratio = 0 if fg_indices.size == 0 else 1

[wyli]

thanks for reporting, I'm submitting a patch #5415