[ci skip]

```
PHP Notice – yii\base\ErrorException

Undefined offset: 3

in .../yiisoft/yii2/db/QueryTrait.php at line 269
```

Adjustments code according to the standards.
Adding missing PHPDoc comment.

Fixes #3066: `yii\db\mssql\Schema::getTableSchema()` should return null when the table does not exist.

PHPDoc comment does not match function or method signature
Update PHPDoc Comment

Adjust code standard

issue #3026

fixes #3034

New addSelect method. Useful for scopes.

fixes #2650

Fixes #2955: Changed the signature of ActiveQuery constructors and `ActiveRecord::createQuery()` to simplify customizing ActiveQuery classes

fixes #2957

fix for https://github.com/yiisoft/yii2/pull/2958

Refactored ActiveRecord::find() so that find(null) will also return an ActiveRecord instance instead of ActiveQuery.