[QA] Empty set of results can cause the F1-measure to fail

[MichaelRoeder]

 org.aksw.gerbil.exceptions.GerbilException: java.lang.ArrayIndexOutOfBoundsException: 0
	at org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:599) ~[classes/:?]
	at org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167) [classes/:?]
	at org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44) [topicmodeling.concurrent-0.0.2-20160315.131022-1.jar:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_191]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_191]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
Caused by: java.lang.ArrayIndexOutOfBoundsException: 0
	at org.aksw.gerbil.evaluate.impl.ConfidenceBasedFMeasureCalculator.calculateOptMicroFMeasure(ConfidenceBasedFMeasureCalculator.java:104) ~[classes/:?]
	at org.aksw.gerbil.evaluate.impl.ConfidenceBasedFMeasureCalculator.calculateMicroFMeasure(ConfidenceBasedFMeasureCalculator.java:75) ~[classes/:?]
	at org.aksw.gerbil.evaluate.impl.ClassConsideringFMeasureCalculator.evaluate(ClassConsideringFMeasureCalculator.java:63) ~[classes/:?]
	at org.aksw.gerbil.evaluate.AbstractTypeTransformingEvaluatorDecorator.evaluate(AbstractTypeTransformingEvaluatorDecorator.java:41) ~[classes/:?]
	at org.aksw.gerbil.evaluate.AbstractTypeTransformingEvaluatorDecorator.evaluate(AbstractTypeTransformingEvaluatorDecorator.java:41) ~[classes/:?]
	at org.aksw.gerbil.evaluate.SubTaskEvaluator.evaluate(SubTaskEvaluator.java:46) ~[classes/:?]
	at org.aksw.gerbil.execute.ExperimentTask.evaluate(ExperimentTask.java:618) ~[classes/:?]
	at org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:593) ~[classes/:?]
	... 5 more

• Fix it for QA
• Check KE for the same problem
• Check KBC for the same problem