feat: Added new isset method for ArrayStruct

[Fabian Boensch (En0Ma1259)]

Added a new method, to check whether a property is set or not

[Michel (cyl3x)]

allowNull implies that you want to avoid properties which are null but per type definition not allowed to be - which I think is not good. isset should only check if a property is set, if its set but null its also fine. We should adjust the type definitions if we expect nullable properties

[Fabian Boensch (En0Ma1259)]

allowNull implies that you want to avoid properties which are null but per type definition not allowed to be - which I think is not good. isset should only check if a property is set, if its set but null its also fine. We should adjust the type definitions if we expect nullable properties

Even though a field is, by definition, a required field, it can still be set to null or left blank in the SDK (Criteria->addFields()). The same applies to associations if they have not been added to the Criteria.

So, in order to distinguish whether something is set or is null, we would need to build in such a distinction so that we can react accordingly

To be more correct (not 100%), we need to create a new major version which changes the return values of almost every "Entity" method to nullable