Mirroring upgrade task throws exception if no configuration is present

2020-03-18 16:52:53 [Thread-67] ERROR c.a.sal.core.upgrade.PluginUpgrader - Upgrade failed: argument "src" is null
java.lang.IllegalArgumentException: argument "src" is null
	at com.fasterxml.jackson.databind.ObjectMapper._assertNotNull(ObjectMapper.java:4413)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3315)
	at com.fasterxml.jackson.databind.ObjectMapper$readValue$2.call(Unknown Source)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:136)
	at com.onresolve.scriptrunner.runner.upgrade.RenameOldMirroringPackageUpgradeTask008.doUpgrade(RenameOldMirroringPackageUpgradeTask008.groovy:42)
	at com.atlassian.sal.core.upgrade.PluginUpgrader.doUpgrade(PluginUpgrader.java:72)
	at com.onresolve.scriptrunner.runner.startup.BitbucketPluginUpgrader.apply(BitbucketPluginUpgrader.groovy:23)
	at com.onresolve.scriptrunner.runner.startup.StashStartupManager.runUpgradeTasks(StashStartupManager.groovy:181)
	at com.onresolve.scriptrunner.runner.startup.StashStartupManager.access$0(StashStartupManager.groovy)
	at com.onresolve.scriptrunner.runner.startup.StashStartupManager$_onPluginEnabledEvent_closure1.doCall(StashStartupManager.groovy:110)
	at com.onresolve.scriptrunner.runner.startup.StashStartupManager$_onPluginEnabledEvent_closure1.doCall(StashStartupManager.groovy)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:98)
	at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
	at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:264)
	at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1034)
	at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:41)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:120)
	at com.onresolve.scriptrunner.runner.util.AOPropertyPersister$5.run(AOPropertyPersister.groovy:206)
	at java.lang.Thread.run(Thread.java:748)