update chip config do not handle nicely missing keys

If a key to be updated is missing in the config file then the update script will raise an error, see https://gitlab.cern.ch/atlas-itk/pixel/module/module-qc-analysis-tools/-/blob/main/src/module_qc_analysis_tools/cli/update_chip_config.py?ref_type=heads#L97

This behaviour is problematic in the InjCap case which is missing for some (all?) new V2 FE chips because it was not measured during WP.