Fix coverity issue in block::initEmptyBlock

[lplewa]

Description

getObjectSize should not return values bigger then 2^16-1. We are assigning it's return value, which is 32 bit to 16 bit one, so it is good to assert it anyway.

Fixes # - issue number(s) if exists

Type of change

Choose one or multiple, leave empty if none of the other choices apply

Add a respective label(s) to PR if you have permissions

• [x] bug fix - change that fixes an issue
• [ ] new feature - change that adds functionality
• [ ] tests - change in tests
• [ ] infrastructure - change in infrastructure and CI
• [ ] documentation - documentation update

Tests

• [ ] added - required for new features and some bug fixes
• [x] not needed

Documentation

• [ ] updated in # - add PR number
• [ ] needs to be updated
• [x] not needed

Breaks backward compatibility

• [ ] Yes
• [x] No
• [ ] Unknown

Notify the following users

List users with @ to send notifications

Other information