Add Delete for Me sync support.

core-util/src/main/java/org/signal/core/util/CursorExtensions.kt

@@ -79,11 +79,15 @@ fun <T> Cursor.requireObject(column: String, serializer: IntSerializer<T>): T {
 
 @JvmOverloads
 fun Cursor.readToSingleLong(defaultValue: Long = 0): Long {
+  return readToSingleLongOrNull() ?: defaultValue
+}
+
+fun Cursor.readToSingleLongOrNull(): Long? {
   return use {
     if (it.moveToFirst()) {
-      it.getLong(0)
+      it.getLongOrNull(0)
     } else {
-      defaultValue
+      null
     }
   }
 }