Use AK4PFchs JES uncertainties as fallback, if the specific ones are absent
Following the JME recommendation from https://hypernews.cern.ch/HyperNews/CMS/get/jes/988/1.html - thanks @fbury & HH team!
This allows to use (and fully correlate) JES uncertainties between e.g. AK4 and AK8 jets by passing
uncertaintiesFallbackJetType="AK4PFchs"
for AK8 jets.
Edited by Pieter David