[Bugfix] Files in SubmodelElementLists and NullPointerException when serializing/deserializing empty files

[fvolz]

When a File had an empty value, a NullpointerException would occur in both AASXDeserializer and AASXSerializer. This is now filtered out with file.getValue != null
Additionally, Files in SubmodelElementLists were not included in the fileList. This was fixed by using the Visitor to get all files.

[FrankSchnicke]

Thanks a lot for providing this bugfix. Would it be possible to provide a test case illustrating that the issue has been fixed?

[FrankSchnicke]

If I understand it correctly, the empty files issue is in the AASXSerializer. Would it be possible to move this test case to the TestAASXSerializer? Additionally, the test does not test the issue correctly. After reverting the code in AASX(De)Serializer, emptyFiles still passes.

[fvolz]

If I understand it correctly, the empty files issue is in the AASXSerializer. Would it be possible to move this test case to the TestAASXSerializer? Additionally, the test does not test the issue correctly. After reverting the code in AASX(De)Serializer, emptyFiles still passes.

I fixed the null test to test the issue. The null issue occured for me in the Deserializer, however, the Deserializer tests utilize the Serializer. When I add an empty file in the SerializerTest, no issue occurs.

EDIT: I changed the serializer test to AASFull which leads to java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "path" in the reverted code.
EDIT2: AASFull had 2 files with the same value and no thumbnail leading to assert failures
EDIT3: I could not make changes to AASFull because other tests expect the exact structure. So instead of adding thumbnail to AASFull, I changed the AASXSerializerTest to both test AASSimple with thumbnail and AASFull without thumbnail

[FrankSchnicke]

There are some unused imports now in AASXDeserializer, AASXSerializer & AASXSerializerTest that lead to warnings. Would it be possible to remove them? I will gladly merge after the warnings are removed and the other comment is addressed.

[FrankSchnicke]

Thanks a lot!