Description of problem:
Retrieving of best solution from Kie server right after starting solver may return best solution with initialized score, but without planning variables assigned to planning entities.
For more info see [1].

Version-Release number of selected component (if applicable):
6.3.0.ER2

How reproducible:
Can be simulated using OptaPlanner integration test [2], test method testGetBestSolution(). This error happens just rarely, best reproducing approach was so far to run mentioned test several times in loop (10-30 times).

Steps to Reproduce:
1.
2.
3.

Actual results:
Best solution is returned with initialized score but without planning variables assigned to planning entities.

Expected results:
If planning variables aren't assigned to planning entities yet then score should be null.

Additional info:

[1] https://issues.jboss.org/browse/PLANNER-564
[2] https://github.com/droolsjbpm/droolsjbpm-integration/blob/master/kie-server-parent/kie-server-tests/kie-server-integ-tests-optaplanner/src/test/java/org/kie/server/integrationtests/optaplanner/OptaplannerIntegrationTest.java