fixed null pointer in getunsyncattacks

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

@@ -2005,11 +2005,13 @@ public class HostageDBOpenHelper extends SQLiteOpenHelper {
         for (SyncDevice sDevice : updatedDevices){
             String deviceID = sDevice.getDeviceID();
             Long maxID = deviceMap.get(deviceID);
+            long checkId = -1;
+            if (maxID != null) checkId = maxID.longValue();
             String selectQuery = "SELECT * FROM " + AttackEntry.TABLE_NAME + " A "
                     + " WHERE "
                     +" ( "
                     + " A." + AttackEntry.COLUMN_NAME_DEVICE + " = " + "'" + deviceID + "'"
-                    + " AND " + " A." + AttackEntry.COLUMN_NAME_SYNC_ID + " > " + maxID
+                    + " AND " + " A." + AttackEntry.COLUMN_NAME_SYNC_ID + " > " + checkId
                     + " ) "
                     //+ " GROUP BY " + AttackEntry.TABLE_NAME + "." + AttackEntry.COLUMN_NAME_DEVICE
                     + " ORDER BY " + " A" + "." + AttackEntry.COLUMN_NAME_SYNC_ID + " DESC ";