Don't throw exception on empty line in CPUs file.

Empty line in CPUs file is a valid use case and the CpuInfoReader must
not throw exception. It should gracefully handle this case.

Cherry picked I9d1b97c9ff0791d1ac49d333cd75656432ccabe2 to master due to b/286408867.

Code was merged via `-s ours` and is missing even though the sha exists on the target branch. Cherry pick is required to bring in the code.

Manually remove the "Merged in" directive to allow for downstream propagation.

Test: atest CpuInfoReaderTest
Fixes: 284537086
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:fe20e634351512d9be270830d4fc66345ddfe6b4)
Change-Id: Ifc5f1614fc4c70e3d0e5ee753d9ba1ac2ab48417