[lldb] Fix AppleObjCDeclVendor for classes which have no methods (#145452)

Fix the rare case where an ObjC class has ivars but no methods. The fix is to not early
return when a class has no method list.

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCClassDescriptorV2.cpp

@@ -552,9 +552,8 @@ bool ClassDescriptorV2::Describe(
     } else {
       std::optional<method_list_t> base_method_list =
           GetMethodList(process, class_ro->m_baseMethods_ptr);
-      if (!base_method_list)
-        return false;
-      if (!ProcessMethodList(instance_method_func, *base_method_list))
+      if (base_method_list &&
+          !ProcessMethodList(instance_method_func, *base_method_list))
         return false;
     }
   }