[NNC] Fix the uninitialized pointer in loopnest.fuse_loops (#59411)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59411
Bug: the uninitialized For* caused a casting error in pybind11.
Test Plan: Imported from OSS
Reviewed By: ZolotukhinM
Differential Revision: D28882635
Pulled By: huiguoo
fbshipit-source-id: e3f2b659bae94e9617936b1b2368157bed73c2fe
