title: Error in OptaPlannerBenchmarkAutoConfiguration fallback case for benchmark?
body: <p>The following question refers to optaplanner version 8.24.1.Final:<br />
  <br />
  In class OptaPlannerBenchmarkAutoConfiguration of package org.optaplanner.spring.boot.autoconfigure there is a fallback in line 61. <br />
  Line 61 calls createFromSolverConfig in class PlannerBenchmarkConfig of package org.optaplanner.benchmark.config which in line 85 sets a single new SolverBenchmarkConfig for field solverBenchmarkConfigList of plannerBenchmarkConfig.
  All fields in this SolverBenchmarkConfig are null.<br />
  Now moving further to line 93 of class OptaPlannerBenchmarkAutoConfiguration, there is a get on SolverConfig. But the field SolverConfig of the new SolverBenchmarkConfig described above is null. This throws a Nullpointerexception. <br />
  Is this intentional? If yes, why? <br />
  <br />
  Admittedly it does seem a bit nonsensical to add the dependency of optaplanner-benchmark while not providing configuration for different solvers to benchmark, but then why even have this fallback? Am I missing something obvious?</p>
  <p>Kind regards and thanks for your help!</p>