Animal Sniffer crashes before processing all files.

[JakeWharton]

Caused by: java.lang.NullPointerException
    at org.codehaus.mojo.animal_sniffer.SignatureChecker$CheckingVisitor.find(SignatureChecker.java:502)
    at org.codehaus.mojo.animal_sniffer.SignatureChecker$CheckingVisitor.access$900(SignatureChecker.java:280)
    at org.codehaus.mojo.animal_sniffer.SignatureChecker$CheckingVisitor$1.check(SignatureChecker.java:416)
    at org.codehaus.mojo.animal_sniffer.SignatureChecker$CheckingVisitor$1.visitMethodInsn(SignatureChecker.java:377)
    at org.objectweb.asm.ClassReader.readCode(ClassReader.java:1429)
    at org.objectweb.asm.ClassReader.readMethod(ClassReader.java:1017)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:693)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:506)
    at org.codehaus.mojo.animal_sniffer.SignatureChecker.process(SignatureChecker.java:195)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processClassFile(ClassFileVisitor.java:176)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:101)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:81)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processDirectory(ClassFileVisitor.java:119)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:97)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:81)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processDirectory(ClassFileVisitor.java:119)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:97)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:81)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processDirectory(ClassFileVisitor.java:119)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:97)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:81)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processDirectory(ClassFileVisitor.java:119)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:97)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:81)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.processDirectory(ClassFileVisitor.java:119)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor.process(ClassFileVisitor.java:97)
    at org.codehaus.mojo.animal_sniffer.ClassFileVisitor$process.call(Unknown Source)
    at io.reactivex.backport.plugin.AnimalSnifferTask.run(AnimalSnifferTask.groovy:32)
    at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.doExecute(AnnotationProcessingTaskFactory.java:226)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:219)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:208)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:585)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:568)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
    ... 14 more