[SIGMON-145] do not crash

Context

• task: https://its.cern.ch/jira/browse/SIGMON-145
• lhc-sm-api MR: lhc-sm-api!96 (merged)
• lhc-sm-notebook MR: lhc-sm-notebook!8 (merged)

What was done

• 'safe' version of pandas.loc/get used in the notebooks

TODO

• ?

QA

• sonar: http://sonar.cern.ch/project/issues?branch=SIGMON-145_do_not_crash&id=lhc-sm-api&resolved=false
• code was not unit tested because it's lhc-sm-hwc
• reference notebooks were reviewed

Review objectives

• sssessment of code functionality
• assessment of code quality
• identifying potential refactorings / logic common to other projects
• knowledge sharing