Stripe test mode is not working

**Describe the bug**
When configuring a test api_key and secret the payment fails

**To Reproduce**
Steps to reproduce the behavior:
1. Configure stripe payment (with a test api key)
2. Create an avent with fee
3. From public front end try to buy the ticket with credit card (stripe)
4. Insert the test card number (4242 4242 4242 4242)
5. An error will be raised

**Expected behavior**
Transaction sould be completed (test mode)

**Screenshots**
This is the warning message on credit card popup

**Desktop (please complete the following information):**
- OS: any
- Browser : any
- Version : any

**Additional context**
*Stack strace info:*
17:51:24.187 [qtp592207425-22] ERROR alfio.manager.TicketReservationManager - unexpected error during payment confirmation
org.springframework.dao.EmptyResultDataAccessException: Incorrect result size: expected 1, actual 0
at org.springframework.dao.support.DataAccessUtils.nullableSingleResult(DataAccessUtils.java:97) ~[spring-tx-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.queryForObject(NamedParameterJdbcTemplate.java:237) ~[spring-jdbc-5.2.5.RELE
ASE.jar:5.2.5.RELEASE]
at ch.digitalfondue.npjt.QueryType.handleSingleObject(QueryType.java:177) ~[npjt-extra-2.0.3.jar:?]
at ch.digitalfondue.npjt.QueryType.access$700(QueryType.java:51) ~[npjt-extra-2.0.3.jar:?]
at ch.digitalfondue.npjt.QueryType$2.doQuery(QueryType.java:117) ~[npjt-extra-2.0.3.jar:?]
at ch.digitalfondue.npjt.QueryType$2.apply(QueryType.java:87) ~[npjt-extra-2.0.3.jar:?]