#67 if no examples are set PosNegLP throws a Nullpointer.

[Sebastian Hellmann]

if no examples are set PosNegLP throws a Nullpointer, but it should actually throw a ComponentInitexception.

Additionally, there is no warning, when the pos and negative Examples overlap:
PosNegLPStandard lp = cm.learningProblem(PosNegLPStandard.class, rc);
lp.setPositiveExamples(posExamples);
lp.setNegativeExamples(posExamples);
silently continues.

WARN [main] (DBpediaClassLearnerCELOE.java:94) -
java.lang.NullPointerException
at org.dllearner.utilities.Helper.union(Helper.java:263)
at org.dllearner.learningproblems.PosNegLP.init(PosNegLP.java:137)
at org.dllearner.learningproblems.PosNegLPStandard.init(PosNegLPStandard.java:87)
at org.dllearner.scripts.improveWikipedia.DBpediaClassLearnerCELOE.learnClass(DBpediaClassLearnerCELOE.java:144)
at org.dllearner.scripts.improveWikipedia.DBpediaClassLearnerCELOE.learnAllClasses(DBpediaClassLearnerCELOE.java:83)
at org.dllearner.scripts.improveWikipedia.DBpediaClassLearnerCELOE.main(DBpediaClassLearnerCELOE.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:115)