Fix null pointer when fetching positions

app/src/main/java/com/todoroo/astrid/gtasks/api/GtasksInvoker.kt

@@ -94,7 +94,7 @@ class GtasksInvoker {
 
     @Throws(IOException::class)
     suspend fun getAllPositions(
-            listId: String?, pageToken: String?): com.google.api.services.tasks.model.Tasks =
+            listId: String?, pageToken: String?): com.google.api.services.tasks.model.Tasks? =
             execute(
                 service!!
                         .tasks()
@@ -103,7 +103,7 @@ class GtasksInvoker {
                         .setShowDeleted(false)
                         .setShowHidden(false)
                         .setPageToken(pageToken)
-                        .setFields("items(id,parent,position),nextPageToken"))!!
+                        .setFields("items(id,parent,position),nextPageToken"))
 
     @Throws(IOException::class)
     suspend fun createGtask(

app/src/main/java/org/tasks/gtasks/GoogleTaskSynchronizer.kt

@@ -158,11 +158,10 @@ class GoogleTaskSynchronizer @Inject constructor(
         var nextPageToken: String? = null
         do {
             val taskList = gtasksInvoker.getAllPositions(listId, nextPageToken)
-            val items = taskList.items
-            if (items != null) {
-                tasks.addAll(items)
+            taskList?.items?.let {
+                tasks.addAll(it)
             }
-            nextPageToken = taskList.nextPageToken
+            nextPageToken = taskList?.nextPageToken
         } while (!isNullOrEmpty(nextPageToken))
         return tasks
     }