update device sync ids where attack_syncid not null

src/de/tudarmstadt/informatik/hostage/persistence/HostageDBOpenHelper.java

@@ -382,7 +382,7 @@ public class HostageDBOpenHelper extends SQLiteOpenHelper {
     synchronized public void updateSyncDevicesMaxID(SQLiteDatabase db){
         HashMap<String, Long> deviceIDmap = new HashMap<String, Long>();
 
-        String selectQuery = "SELECT "+AttackEntry.COLUMN_NAME_DEVICE+ ","+ AttackEntry.COLUMN_NAME_SYNC_ID+" FROM " + AttackEntry.TABLE_NAME + " A "  + " GROUP BY " + AttackEntry.COLUMN_NAME_DEVICE + " HAVING " + AttackEntry.COLUMN_NAME_SYNC_ID + " = MAX( " + AttackEntry.COLUMN_NAME_SYNC_ID + " )";
+        String selectQuery = "SELECT "+AttackEntry.COLUMN_NAME_DEVICE+ ","+ AttackEntry.COLUMN_NAME_SYNC_ID+" FROM " + AttackEntry.TABLE_NAME + " A " + " WHERE " + AttackEntry.COLUMN_NAME_SYNC_ID + " NOT NULL "  + " GROUP BY " + AttackEntry.COLUMN_NAME_DEVICE + " HAVING " + AttackEntry.COLUMN_NAME_SYNC_ID + " = MAX( " + AttackEntry.COLUMN_NAME_SYNC_ID + " )";
 
         {
             Cursor cursor = db.rawQuery(selectQuery, null);