DX-61688 fixed out_len value for nullptr

[xxlaykxx]

In case when when function return nullptr, *out_len value was not updated to 0;
Some explanation:
https://stackoverflow.com/questions/19390136/what-can-cause-a-java-native-function-in-c-to-segfault-upon-entry;
https://docs.oracle.com/en/java/javase/11/vm/error-reporting.html#GUID-2A43EBDE-5EF0-4E6D-AEB6-D6F4B08D8B0C

[github-actions]

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