Fix checkInvalidSuppress.py empty file handling
Fix checkInvalidSuppress.py empty file handling

Test: ./scripts/checkInvalidSuppress.py ./core/src/main/java/androidx/core/text/HtmlCompat.java ./foo/bar/doesntexist.java

Also remove usage of global var

Change-Id: Id74093935b2c83cd0961b26970ecdf9a04903389

androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx