Unit test error after update

[prolic]

There was 1 error:

1) ProophTest\EventStore\Projection\PostgresEventStoreProjectionTest::it_links_to_and_loads_and_continues_again

Prooph\EventStore\Exception\ConcurrencyException: 

/home/travis/build/prooph/pdo-event-store/src/PostgresEventStore.php:157

/home/travis/build/prooph/pdo-event-store/vendor/prooph/common/src/Event/ProophActionEventEmitter.php:63

/home/travis/build/prooph/pdo-event-store/vendor/prooph/event-store/src/AbstractActionEventEmitterEventStore.php:54

/home/travis/build/prooph/pdo-event-store/vendor/prooph/event-store/src/Projection/AbstractProjection.php:64

/home/travis/build/prooph/pdo-event-store/vendor/prooph/event-store/src/Projection/AbstractProjection.php:137

/home/travis/build/prooph/pdo-event-store/tests/Projection/PostgresEventStoreProjectionTest.php:91

/home/travis/build/prooph/pdo-event-store/vendor/prooph/event-store/src/Projection/AbstractQuery.php:208

/home/travis/build/prooph/pdo-event-store/vendor/prooph/event-store/src/Projection/AbstractProjection.php:99

/home/travis/build/prooph/pdo-event-store/src/Projection/AbstractPDOProjection.php:73

/home/travis/build/prooph/pdo-event-store/tests/Projection/PostgresEventStoreProjectionTest.php:95