Fixes in GRP DCS processor

[shahor02]

Warn about empty collimator or env.vars object.
Protection in resetAndKeepLast agains empty vectors

[github-actions]

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[alibuild]

Error while checking build/O2/fullCI for 83f57da at 2024-03-20 02:50:

## sw/BUILD/O2-latest/log
c++: error: unrecognized command-line option '--rtlib=compiler-rt'
c++: error: unrecognized command-line option '--rtlib=compiler-rt'


## sw/BUILD/O2-full-system-test-latest/log
task timeout reached .. killing all processes


## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
++ GRERR=1
++ [[ 1 == 0 ]]
++ mkdir -p /sw/INSTALLROOT/dd4bd6ae5c65bd4211560d30795a6a0d959a647f/slc8_x86-64/o2checkcode/1.0-local249/etc/modulefiles
++ cat
--

Full log here.