Fix exception throwing - Close 942

[alepop]

What was the problem?

If file in appData folder is corrupted (storage/config.json) it causes an error on Lisk Nano launch.
It happens because electron-json-storage expects file with valid json format, but file can be empty.

How did I fix it?

Remove throw error code.

How to test it?

Try to open and close Lisk Nano many times before full loading is completed.

Review checklist

• The PR solves Lisk Nano throw an error if config.json is corrupted #942
• All new code is covered with unit tests
• All new features are covered with e2e tests
• All new code follows best practices

[slaweet]

Thank you @alepop