ci: Use default blank if no TEST_CONFIG (#69008)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69008
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>
Test Plan: Imported from OSS
Reviewed By: malfet
Differential Revision: D32699051
Pulled By: seemethere
fbshipit-source-id: 9ed12fe8a7f541c6eda77182cfd1b0a733a545f0
