Do not access not-existing properties

[thePanz]

Q	A
Bug fix?	yes/no
New feature?	no
Doc updated	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes/no
License	MIT

This also checks that the accessor is not trying to access a property that does not exist on the object. See the getValue() with return $o->$name ?? null;

This is happening in the following case:

 class ClassA {
    /**
     * @var ClassB[]|null
     * @Type("array<App\Model\ClassB>")
     */
    public $sortimentierungen;
}

class ClassB {
    /**
     * @var string|null
     * @Type("string")
     */
    public $code;
}

And we deserialize from an XML like:

<ClassA>
  <ClassB />
  <ClassB><code>123</code></ClassB>
</ClassA>

The first element of type ClassB is defined, but with no properties: this leads the serializer trying to read from a not existing property stdClass->code. And getting the PHP notice Notice: Undefined property: stdClass::$code.

[goetas]

Thanks for the PR!
Much appreciated!

This also checks that the accessor is not trying to access a property that does not exist on the object. See the getValue() with return $o->$name ?? null;

Can you create a test case for this?

[thePanz]

I am trying to create a test case for this, mimicking the bug I had in my project.
Looks like it is more complicated than I expected, I'll post an update ASAP :)

[thePanz]

@goetas looks like the whole issue was caused by a weird data being serialized.
The property @var Classb[] was an array, but of a different class.

I will try to alter this MR to provide a better exception reporting the class mismatch, so to help to identify the issue