1868-fix-potential-inf-in-lncc-loss (#1915)
1868-fix-potential-inf-in-lncc-loss (#1915)

* clip variance to be >= 0

Signed-off-by: kate-sann5100 <89732a8c80bcb4e474b98d52cd6224c499dd9cc3@st-annes.ox.ac.uk>

* max for torch1.6

Signed-off-by: Wenqi Li <8ba7dfe933ef10910139377fbe2efeb7f8f88b49@nvidia.com>

Co-authored-by: Wenqi Li <8ba7dfe933ef10910139377fbe2efeb7f8f88b49@nvidia.com>
Project-MONAI/MONAI,Project-MONAI/MONAI,Project-MONAI/MONAI,Project-MONAI/MONAI