JSON reader fails in case of empty bytes field

[mikir]

What version of Zserio and what language are you using?
Zserio: 2.13.0
Language: Python, Java, C++

Describe the bug
If JSON file contains empty bytes field, e.g.

"myBytes": {
                "buffer": [
                ]
           }

the JSON reader in Python throws exception:

zserio.exception.PythonRuntimeException: JsonReader: Unexpected end in bytes!

To Reproduce
Just create schema with empty bytes field, write it to JSON and read it again.

Expected behavior
No exception.

Additional context:
The same problem is for C++ and Java.

[mikir]

See related #581.