DtsApi.getInterfaces - Exception in thread "main" java.lang.NullPointerException

This happens with only a few jar files, but I get this error when throwing them through the dts-generator:

Exception in thread "main" java.lang.NullPointerException
	at com.telerik.dts.DtsApi.getInterfaces(DtsApi.java:352)
	at com.telerik.dts.DtsApi.generateDtsContent(DtsApi.java:75)
	at com.telerik.dts.Generator.generateDts(Generator.java:37)
	at com.telerik.dts.Generator.start(Generator.java:29)
	at com.telerik.Main.main(Main.java:21)

I've found that adding a check if clazz1 != null allows the generator to work.
JavaClass clazz1 = ClassRepo.findClass(intface);
The fix source:
https://github.com/roblav96/android-dts-generator/commit/1dae5329050ca198977102400cd2a14588f840af#diff-84b371273f2d411517c3ef4981518716

Jar Examples

Download jars here:
https://drive.google.com/file/d/0BzsNfWSNiUKLRlNOWkctb1JvZ1E/view?usp=sharing

OneSignal

java -jar dts-generator-debug.jar \
-input android24.jar \
-input android-support-v4.jar \
-input android-support-v7-appcompat.jar \
-input amazon-device-messaging-1.0.1.jar \
-input OneSignalSDK.jar \
-generate-multiple

materialdrawer

java -jar dts-generator.jar \
-input android24.jar \
-input android-support-v4.jar \
-input android-support-v7-appcompat.jar \
-input android-support-v7-recyclerview.jar \
-input materialize-1.0.0.jar \
-input materialdrawer-5.7.0.jar \
-generate-multiple

Start in DtsApi.java at getInterfaces, especially line 352, then follow generateDtsContent and the Generator entry points shown in the stack trace. Reproduce with the OneSignal or materialdrawer jar command and confirm generation completes without the reported NullPointerException. The issue includes an external commit showing a possible fix to compare against.