NullPointerException during upgrade

Question

Not able to upgrade Jahia. Here is the error when applying fix

java.lang.NullPointerException
at java.util.TreeMap.getEntry(Unknown Source)
at java.util.TreeMap.containsKey(Unknown Source)
at org.jahia.fixapplier.controller.ModuleHandler.loadDeployedModules(ModuleHandler.java:311)
at org.jahia.fixapplier.controller.ModuleHandler.loadModules(ModuleHandler.java:434)
at org.jahia.fixapplier.controller.FixApplierController.patch(FixApplierController.java:1114)
at org.jahia.fixapplier.controller.FixApplierController.startSession(FixApplierController.java:294)
at org.jahia.fixapplier.Application.main(Application.java:295)

Cause

Custom jars present in <digital-factory-data>/modules folder

Solution

Remove any custom jar in <digital-factory-data>/modules folder and un the upgrade again.