filterAllActivities broken in 2015 Update 1

In CRM Dynamics 2015 Online, I have been using the following code as an onload event on the account forms to set the default filter to 'All' for the Open Activities Associated View:

//default the Activities 'Filter on' to 'All' for Account and Contact for rollup 12
function filterAllActivities() {
    document.getElementById("nav_Activities").onclick = function () {
        Mscrm.Details.loadArea(this, "areaActivities");

        document.getElementById("areaActivitiesFrame").onload = function () {
            var entityName = Xrm.Page.data.entity.getEntityName();
            var entity = entityName.charAt(0).toUpperCase() + entityName.substr(1);
            var doc = this.contentWindow.document;
            var filterOn = doc.getElementById("crmGrid_" + entity + "_ActivityPointers_datefilter");

            filterOn.value = "All";

            var evt = document.createEvent("HTMLEvents");
            evt.initEvent("change", false, true);
            filterOn.dispatchEvent(evt);
        };
    };
}

This has been working like a charm. However - Yesterday we got the new update to CRM Online 2015, and now when I load my account forms it errors out with this:

TypeError: Unable to set property 'onclick' of undefined or null reference
   at filterAllActivities (metacompliance.crm4.dynamics.com/.../new_filteraccountactivities)
   at eval code (eval code:1:1)
   at RunHandlerInternal (metacompliance.crm4.dynamics.com/.../ClientApiWrapper.aspx:142:1)
   at RunHandlers (metacompliance.crm4.dynamics.com/.../ClientApiWrapper.aspx:101:1)
   at OnScriptTagLoaded (metacompliance.crm4.dynamics.com/.../ClientApiWrapper.aspx:215:1)
   at Anonymous function (metacompliance.crm4.dynamics.com/.../ClientApiWrapper.aspx:186:1)

Obviously I can disable the event and it all works fine - but I really liked the All filter as it suits everything we do. Has anyone been able to get this working in the latest version?

Thanks

Noel