Using soft deleteAll endpoint throws exception on unknown id

[olliefreeman]

If an unknown id is included in the list of ids to be deleted and permanent is false then an NPE is thrown

{
    "status": 500,
    "reason": "Internal Server Error",
    "errorCode": "UEX--",
    "message": "Cannot invoke method getDirtyPropertyNames() on null object",
    "path": "/api/codeSets",
    "environment": "DEVELOPMENT",
    "version": "5.1.0-SNAPSHOT",
    "exception": {
        "type": "NullPointerException",
        "message": "Cannot invoke method getDirtyPropertyNames() on null object",
        "stacktrace": [
            "uk.ac.ox.softeng.maurodatamapper.core.controller.ModelController.updateResource(ModelController.groovy:765)",
            "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)",
            "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
            "uk.ac.ox.softeng.maurodatamapper.core.controller.ModelController$__tt__deleteAll_closure23.doCall(ModelController.groovy:714)",
            "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)",
            "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
            "uk.ac.ox.softeng.maurodatamapper.core.controller.ModelController.$tt__deleteAll(ModelController.groovy:713)",
            "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)",
            "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
            "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)",
            "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
            "grails.gorm.transactions.GrailsTransactionTemplate$2.doInTransaction(GrailsTransactionTemplate.groovy:94)",
            "org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)",
            "grails.gorm.transactions.GrailsTransactionTemplate.execute(GrailsTransactionTemplate.groovy:91)",
            "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)",
            "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
            "org.grails.core.DefaultGrailsControllerClass$ReflectionInvoker.invoke(DefaultGrailsControllerClass.java:211)",
            "org.grails.core.DefaultGrailsControllerClass.invoke(DefaultGrailsControllerClass.java:188)",
            "org.grails.web.mapping.mvc.UrlMappingsInfoHandlerAdapter.handle(UrlMappingsInfoHandlerAdapter.groovy:90)",
            "org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)",
            "org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)",
            "org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)",
            "org.springframework.web.servlet.FrameworkServlet.doDelete(FrameworkServlet.java:931)",
            "org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)",
            "org.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:77)",
            "org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:67)",
            "java.lang.Thread.run(Thread.java:833)"
        ]
    }
}