Do not crash if class is defined in wrong scope.

This patch fixes PR16677. The latter represents the case when due to
misprinted character class definition occurs in the scope of template
arguments. Base class of this class depends on the template parameter in the
same scope and cannot be resolved, it causes crash. Right behavior is to
make semantic processing even if the definition is wrong, as the code
that emits appropriate message is called after the processing.

llvm-svn: 256511