Execution of JApiCmp failed: Optional.get() with 0.7.1 and 0.7.2

[ccz99]

I hit the below exception with 0.7.1 and 0.7.2. But there is no issue with 0.7.0. So a regression should be introduced here.

Execution of JApiCmp failed: Optional.get() cannot be called on an absent value
java.lang.IllegalStateException: Optional.get() cannot be called on an absent value
at com.google.common.base.Absent.get(Absent.java:47)
at japicmp.model.JApiException.isCheckedException(JApiException.java:25)
at japicmp.model.JApiException.(JApiException.java:18)
at japicmp.model.JApiBehavior.computeExceptionChanges(JApiBehavior.java:66)
at japicmp.model.JApiBehavior.(JApiBehavior.java:53)
at japicmp.model.JApiMethod.(JApiMethod.java:17)
at japicmp.model.JApiClass.sortMethodsIntoLists(JApiClass.java:329)
at japicmp.model.JApiClass.computeMethodChanges(JApiClass.java:304)
at japicmp.model.JApiClass.(JApiClass.java:51)
at japicmp.cmp.ClassesComparator.sortIntoLists(ClassesComparator.java:50)
at japicmp.cmp.ClassesComparator.compare(ClassesComparator.java:30)
at japicmp.cmp.JarArchiveComparator.compareClassLists(JarArchiveComparator.java:183)
at japicmp.cmp.JarArchiveComparator.createAndCompareClassLists(JarArchiveComparator.java:161)
at japicmp.cmp.JarArchiveComparator.compare(JarArchiveComparator.java:72)
at japicmp.cli.JApiCli$Compare.run(JApiCli.java:74)
at japicmp.JApiCmp.main(JApiCmp.java:16)

[siom79]

Since 0.7.1 exceptions are loaded from the classpath. If this fails, you currently see the above error message. Improved this on the develop branch.