[preprocessor] fixed the exception catching when landmarks are not detected (PPGSecure)

4 jobs for debug-pulse-based-pad in 14 minutes and 47 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #142995
docker
build_linux_27

00:14:46

56.0%
passed #142996
docker
build_linux_36

00:14:46

56.0%
passed #142997
macosx
build_macosx_27

00:13:33

56.0%
passed #142998
macosx
build_macosx_36

00:12:48

56.0%