DNU in browser when selecting Selector → Compare menu

[vranyj1]

...when fake/virtual missing method is selected (such as one in pseudo-category required).

Steps to reproduce:

1. Create class ClassA.
2. Define method foo in ClassA as subclass responsibility.
3. Create class ClassB as a subclass of ClassA
4. In browser, you should see a pseudo category required (1), select it.
5. Select missing method (labeled as foo (* * missing required * *) in red)
6. From main menu select Selector → Compare

As soon as the pointer in over Compare item, a DNU is thrown
becase the method is actually unbound.

[Jan Vrany]

Fixed in Tools::MethodCategoryList?. rev 1.100