procinfo: do null check before setting error string. am: cf2bd921df

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/libprocinfo/+/14629892

Change-Id: I40dc02ce42b917c9604b2d877e6ee39309f4f928
tree: 6b2000fa0bafa5a0e27b839d62c2e29c63428375
  1. include/
  2. testdata/
  3. Android.bp
  4. OWNERS
  5. process.cpp
  6. process_map_benchmark.cpp
  7. process_map_test.cpp
  8. process_test.cpp