Optimise PIM page a bit more.

src/Pim.tsx

@@ -51,10 +51,10 @@ const itemsSelector = createSelector(
         const collectionInfo = syncJournal.collection;
 
         if (collectionInfo.type === 'ADDRESS_BOOK') {
-          addressBookItems = Object.assign(addressBookItems, syncEntriesToItemMap(collectionInfo, syncEntries));
+          addressBookItems = syncEntriesToItemMap(collectionInfo, syncEntries, addressBookItems);
           collectionsAddressBook.push(collectionInfo);
         } else if (collectionInfo.type === 'CALENDAR') {
-          calendarItems = Object.assign(calendarItems, syncEntriesToCalendarItemMap(collectionInfo, syncEntries));
+          calendarItems = syncEntriesToCalendarItemMap(collectionInfo, syncEntries, calendarItems);
           collectionsCalendar.push(collectionInfo);
         }
       }

src/journal-processors.tsx

@@ -6,8 +6,9 @@ import { EventType, ContactType } from './pim-types';
 
 import * as EteSync from './api/EteSync';
 
-export function syncEntriesToItemMap(collection: EteSync.CollectionInfo, entries: List<EteSync.SyncEntry>) {
+export function syncEntriesToItemMap(
-  let items: {[key: string]: ContactType} = {};
+  collection: EteSync.CollectionInfo, entries: List<EteSync.SyncEntry>, base: {[key: string]: ContactType} = {}) {
+  let items = base;
 
   entries.forEach((syncEntry) => {
     let comp = new ContactType(new ICAL.Component(ICAL.parse(syncEntry.content)));
@@ -49,8 +50,9 @@ function colorIntToHtml(color: number) {
     ((alpha > 0) ? toHex(alpha) : '');
 }
 
-export function syncEntriesToCalendarItemMap(collection: EteSync.CollectionInfo, entries: List<EteSync.SyncEntry>) {
+export function syncEntriesToCalendarItemMap(
-  let items: {[key: string]: EventType} = {};
+  collection: EteSync.CollectionInfo, entries: List<EteSync.SyncEntry>, base: {[key: string]: EventType} = {}) {
+  let items = base;
 
   const color = colorIntToHtml(collection.color);