Fix exception if input test is not a real module

Add check for is_tradefed_testable_module() if input mod-info is None to
prevent exception happend.

Bug: 271223457
Test: m atest ; atest-dev HelloWorldTests
Test: m atest ; atest-dev native-benchmark

Change-Id: I951c6282dc41eb436bda399be1e209e4ca783fd7
1 file changed