Accessing a Page Edit screen returns the following between the Name & the URL, however this issue likely can be caused in more places where the get_var function does not return a row.
Notice: Trying to access array offset on value of type null in <dir>\html\wp-includes\wp-db.php on line 2612 (Please note the line maybe slightly off due to a minor edit within our config)

	if(false === $result)
		return null;

	$row = sqlsrv_fetch_array( $result );
	return $row[ 0 ];   // <---- This line
}

"SELECT TOP 1 post_name FROM wp_posts WHERE post_name = '<POSTNAME>' AND post_type IN ( 'page', 'attachment' ) AND ID != 5227 AND post_parent = 4882"
is the Failing SQL Query in my case. This is likely to no rows returned and can be fixed by changing it to:

Fix

return sqlsrv_has_rows( $result ) ? $row[ 0 ] : null;

or however else you'd prefer.

Currently at work so can make a basic PR Request later fixing this issue.

Edit: Information

SQLSRV: 5.9.0+14116
PHP: 7.4.15 (NTS)
Nami: 5.7.2 (recent update from 5.3.2)