[TASK] Drop redundant constructor code

[oliverklee]

• use default values for properties instead of setting them in the constructor
• drop constructors that are redundant to the constructor of the parent class

[coveralls]

coverage: 50.453% (-0.05%) from 50.498%
when pulling b7989b0 on cleanup/drop-redundant-constructors
into e1fa3b6 on main.

[JakeQZ]

Only had a brief look at this. Initializing properties to null is not necessary since that is the default, and by convention this is not normally explicitly done.

I found https://stackoverflow.com/questions/13114602/are-parent-constructors-called-if-a-child-class-does-not-define-a-constructor#13114603 which confirms constructors can be removed provided the base class defines one.

[oliverklee]

Done and repushed.

[JakeQZ]

I think this works now.

IIRC, the PHP language issue with undefined constructors is when there is a base class with no constructor defined:

• the derived class cannot call parent::__construct();
• if the base class is later modified to add a constructor to perform an important initialization task, it won't be implicitly called;
• to mitigate against this, the base class should have an empty constructor from the outset, so that the derived class can call it, should it later need to do something.
• (C++ does not have this problem because default constructors are always implicitly called.)

The issue doesn't apply here, since all the removed constructors are in derived classes for which there is a already a constructor in the base class.