[5.2] PostgresProcessor::processInserGettId | array cast fails to get Id when PDO fetch mode is set to PDO::FETCH_CLASS

[melloc01]

function processInsertGetId

How to reproduce:

• Enable PDO fetch mode set to PDO::FETCH_CLASS choosing it to cast to a Class that does not have the attributes set directly to the object, like Eloquent models that uses the $attributes property
• Use processInsertGetId

Description:
Casting the $results[0] to an array having PDO fetch mode set to PDO::FETCH_CLASS and the chosen class implements magic methods to handle attributes getters and setters (like Eloquent Models) the function would throw an error Undefined index {$sequence} on the assignment:

$id = $result[$sequence];

The problem occurs because the given object would be cast to an array that doesn't have the "id" key on its first level of keys.

About the solution:
On my use cases $result is always an object (on any PDO fetch method) but I still tested it because I was not sure I was covering all the use cases.

Feel free to comment, improve or create a test for this function & PR.

[vlakoff]

Looks good to me. Also you have inspired me #14121 :)