message: Fix a crash in dynamic type resolution.
  This was found by TestSwiftExpressionsInClassFunctions.py
diff: @@ -475,14 +475,16 @@ public:
  return;
  }
  - // In the case where the value is of Swift generic type, we need to unbox
  - // it
  + // In the case where the value is of Swift generic type, unbox it.
  CompilerType valobj_type = valobj_sp->GetCompilerType();
  if (m_is_generic) {
  - valobj_sp = valobj_sp->GetDynamicValue(lldb::eDynamicDontRunTarget);
  - valobj_type = valobj_sp->GetCompilerType(); // update the type to refer to
  - // the dynamic type
  + auto dyn_obj = valobj_sp->GetDynamicValue(lldb::eDynamicDontRunTarget);
  + if (dyn_obj) {
  + // Update the type to refer to the dynamic type.
  + valobj_sp = dyn_obj;
  + valobj_type = valobj_sp->GetCompilerType();
  + }
  }
  if (m_is_reference) {
  