Add nullable annotation to googletask/caldav lists

app/src/main/java/com/todoroo/astrid/adapter/CaldavTaskAdapter.kt

@@ -29,11 +29,11 @@ open class CaldavTaskAdapter internal constructor(private val taskDao: TaskDao,
         val newParent = changeParent(task, indent, to)
         if (newParent != task.parent) {
             val newPosition = if (newTasksOnTop) {
-                caldavDao.findFirstTask(task.caldav, newParent)
+                caldavDao.findFirstTask(task.caldav!!, newParent)
                         ?.takeIf { task.creationDate.toAppleEpoch() >= it}
                         ?.minus(1)
             } else {
-                caldavDao.findLastTask(task.caldav, newParent)
+                caldavDao.findLastTask(task.caldav!!, newParent)
                         ?.takeIf { task.creationDate.toAppleEpoch() <= it }
                         ?.plus(1)
             }

app/src/main/java/com/todoroo/astrid/adapter/GoogleTaskAdapter.kt

@@ -53,7 +53,7 @@ open class GoogleTaskAdapter internal constructor(private val taskDao: TaskDao,
         }
         taskDao.touch(task.id)
         if (BuildConfig.DEBUG) {
-            googleTaskDao.validateSorting(task.googleTaskList)
+            googleTaskDao.validateSorting(task.googleTaskList!!)
         }
     }
 }

app/src/main/java/com/todoroo/astrid/adapter/GoogleTaskManualSortAdapter.kt

@@ -31,7 +31,7 @@ class GoogleTaskManualSortAdapter internal constructor(val taskDao: TaskDao, val
         }
         taskDao.touch(task.id)
         if (BuildConfig.DEBUG) {
-            googleTaskDao.validateSorting(task.googleTaskList)
+            googleTaskDao.validateSorting(task.googleTaskList!!)
         }
     }
 }

app/src/main/java/org/tasks/data/CaldavDao.kt

@@ -198,9 +198,9 @@ abstract class CaldavDao {
         val previousPosition = task.caldavSortOrder
         if (newPosition != null) {
             if (newParent == previousParent && newPosition < previousPosition) {
-                shiftDown(task.caldav, newParent, newPosition, previousPosition)
+                shiftDown(task.caldav!!, newParent, newPosition, previousPosition)
             } else {
-                shiftDown(task.caldav, newParent, newPosition)
+                shiftDown(task.caldav!!, newParent, newPosition)
             }
         }
         caldavTask.cd_order = newPosition

app/src/main/java/org/tasks/data/TaskContainer.java

@@ -1,5 +1,6 @@
 package org.tasks.data;
 
+import androidx.annotation.Nullable;
 import androidx.room.Embedded;
 import com.todoroo.astrid.data.Task;
 import java.util.Objects;
@@ -21,12 +22,20 @@ public class TaskContainer {
     return tags;
   }
 
-  public String getGoogleTaskList() {
-    return googletask == null ? null : googletask.getListId();
+  public @Nullable String getGoogleTaskList() {
+    return isGoogleTask() ? googletask.getListId() : null;
   }
 
-  public String getCaldav() {
-    return caldavTask == null ? null : caldavTask.getCd_calendar();
+  public boolean isGoogleTask() {
+    return googletask != null;
+  }
+
+  public @Nullable String getCaldav() {
+    return isCaldavTask() ? caldavTask.getCd_calendar() : null;
+  }
+
+  public boolean isCaldavTask() {
+    return caldavTask != null;
   }
 
   public String getNotes() {