This patch attempts to fix the attached assert. However, I think
(also discussed with Sven) that this only covers an underlying problem.
So far we investigated the following:
- the method DeclarationNavigationContext::htmlIdentifiedType is called with non-null type and idType
- inside the if-clause, in line 56, the type variable is overwritten with the null type of the computed base class
Thus the question, why/how can the base class have an empty type?
I would be really happy for getting hints on how to debug this. For now,
the patch checks for this case and avoids the crash.