Issue 4127 - [emscripten] Convert subscription classes to C++ - Part 2

compiled/bindings.ipp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 441 matching lines @@
       else
       {
         result += "    var type = HEAP32[result + " + std::to_string(offset)+ " >> 2];\n";
         result += "    if (type in " + cls.name + "_mapping)\n";
         result += "      result = new (exports[" + cls.name + "_mapping[type]])(result);\n";
         result += "    else\n";
         result += "      throw new Error('Unexpected " + cls.name + " type: ' + type);\n";
       }
 
       result += "  }\n";
+      result += "  else\n";
+      result += "    result = null;\n";
       return result;
     }
     else
       throw std::runtime_error("Unexpected return type for " + std::string(call.name));
   }
 
   const std::string wrapCall(const FunctionInfo& call)
   {
     char buffer[20];
     bool hasStringArgs = false;
@@ skipping 284 matching lines @@
 
     std::vector<std::pair<int, std::string>> mapping;
     for (const auto& item : list)
       mapping.emplace_back(item.first, item.second);
 
     bindings_internal::register_differentiator(
         bindings_internal::TypeInfo<ClassType>(), offset, mapping);
     return *this;
   }
 };