Planner: Divide by zero exception on timeMillisSpend on a fast computer

In org.drools.planner.core.localsearch.DefaultLocalSearchSolver::solvingEnded, there is potentially a divide by zero that occurs on the line:

long averageCalculateCountPerSecond = localSearchSolverScope.getCalculateCount() * 1000L / timeMillisSpend;

if timeMillisSpend is zero. Although in theory the likelihood of this occurring in practically nothing, we have actually seen it occur on a POC project with long running Planner jobs. An appropriate guard should be added to this calculation to ensure that this error cannot occur.