bench: Allow skip benchmark

Co-authored-by: Martin Ankerl <Martin.Ankerl@gmail.com>

src/bench/bench.cpp

@@ -70,7 +70,10 @@ void benchmark::BenchRunner::RunAll(const Args& args)
             }
             std::cout << bench.complexityBigO() << std::endl;
         }
-        benchmarkResults.push_back(bench.results().back());
+
+        if (!bench.results().empty()) {
+            benchmarkResults.push_back(bench.results().back());
+        }
     }
 
     GenerateTemplateResults(benchmarkResults, args.output_csv, "# Benchmark, evals, iterations, total, min, max, median\n"