Added alias to from_user field, fixed TypeError

[MasterGroosha]

Description

This fixes TypeError: Value should be instance of 'User' not 'NoneType'

Related: https://t.me/aiogram_ru/489310

Type of change

Please delete options that are not relevant.

• Documentation (typos, code examples or any documentation update)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Desperate Times Call for Desperate Measures, so no tests, except running bot once. You can test it yourself by blocking and unblocking your bot.

Test Configuration:

• Operating System: Manjaro
• Python version: 3.9

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes