issue #126 - don't crash on uninitialized properties

[pounard]

I took the liberty of creating a duplicate of #370 that fixes #126.

I have copy/pasted code from the former, but changed the way the guard is implemented by simply writing the extract this way:

try {
    $ret['possibly_unitialized_property'] = $object->possibly_unitialized_property;
} catch (\Error) {}

Hiding engine errors is probably a terrible thing to do, although it works.

There is a question remaining open, should we instead write this ?

try {
    $ret['possibly_unitialized_property'] = $object->possibly_unitialized_property;
} catch (\Error) {
    $ret['possibly_unitialized_property'] = null;
}

I guess simply not setting the value in the array is more representative of what is happening: the value don't get set in the array since it wasn't set at all in the object. I don't care which is the best, both will work for most my use cases, or can be worked around easily.