Populations of abstract classes are not listed in index

In Grails 4.0.3 and Grails 3.3.11, if you have an inheritance hierarchy with an abstract superclass, e.g.

```{groovy}
package mypackage

abstract class A {
String name
// ...
// properties
// ...
}
```

```{groovy}
package mypackage

class B extends A {
String b
// ...
// properties
// ...
}
```

```{groovy}
package mypackage

class C extends A {
String c
// ...
// properties
// ...
}
```

And you populate the concrete classes in `Bootstrap.groovy`, e.g.

```{groovy}
package mypackage

class BootStrap {

def init = { servletContext ->
A.withTransaction { status ->
def listOfB = []
(1..25).each { i ->
listOfB << new B(name:"b${i}",b:"${i}st")
}

B.saveAll( listOfB )

def listOfC = []
(1..25).each { i ->
listOfC << new C(name:"c${i}",c:"${i}nd")
}

C.saveAll( listOfC )
}
}
def destroy = {
}
}
```

If you use scaffolding, the _index_ page for `A` shows an empty list instead of a paginated list of 50 objects (25 B objects and other 25 C objects).

Apart from that, it shows a _new_ button that generates a `java.lang.InstantiationException` when clicked because it tries to instantiate an abstract class.

A quick and dirty workaround for this problem is the following:

1. Generate views for the abstract class (only `index.gsp` is relevant)
2. Edit the generated `index.gsp` in the following way:

* Comment the _new_ button code
```{html}

```

* Comment the `` element and add the following code
```{html}

```

With respect to `` attributes:
* The `aList` variable originally passed to `` is `null`.
* Do not include `domainClass="mypackage.A"`, it generates a `java.lang.InstantiationException`.
* The `properties` attribute must be present and contain the list of properties of the abstract class **only**. If it is not present, and objects of classes `A` and `B` appear in the same pagination, a `org.springframework.beans.NotReadablePropertyException` is thrown because `` tries to read properties of class `B` on objects of class `C` and viceversa.

Apart from that, the `create` and `edit` pages are still available for `A`. I have `generated-all` for `A` and tried to delete those methods from the generated controller, but my knowledge of Grails is limited and I am having lots of errors with that, so I went back to scaffolding (which is my main reason for using Grails).

I think that Grails should not show empty lists for abstract classes in scaffolding, but I do not know if that behaviour is inside the scaffolding controller, the `` tag, or harcoded in `_table.gsp`.

I also think that Grails should not generate `create` and `update` methods in the scaffolding controllers for abstract classes.

Reproduce the scaffolding case with abstract A and concrete B and C, then trace the generated controller, index.gsp, f:table, and _table.gsp to find where abstract classes are handled. Check the existing create, edit, and update actions as well as index data generation; done means the index lists inherited concrete instances without instantiation or property errors, and abstract-class creation actions are not generated.

Written by the indexing model from the issue text.