Convert references to FileSystem & Co. into shared pointers (avoid use after free)

src/ConsoleJsObject.cpp

 #include <AdblockPlus/JsEngine.h>
 #include <AdblockPlus/JsValue.h>
 #include <AdblockPlus/ErrorCallback.h>
 #include <sstream>
 
 #include "ConsoleJsObject.h"
 
 namespace
 {
   v8::Handle<v8::Value> ErrorCallback(const v8::Arguments& arguments)
   {
     AdblockPlus::JsEngine& jsEngine = AdblockPlus::JsEngine::FromArguments(arguments);
     const AdblockPlus::JsEngine::Context context(jsEngine);
     AdblockPlus::JsValueList converted = jsEngine.ConvertArguments(arguments);
 
     std::stringstream message;
     for (size_t i = 0; i < converted.size(); i++)
       message << converted[i]->AsString();
 
-    (jsEngine.GetErrorCallback())(message.str());
+    AdblockPlus::ErrorCallbackPtr callback = jsEngine.GetErrorCallback();
+    (*callback)(message.str());
     return v8::Undefined();
   }
 
   v8::Handle<v8::Value> TraceCallback(const v8::Arguments& arguments)
   {
     return v8::Undefined();
   }
 }
 
 AdblockPlus::JsValuePtr AdblockPlus::ConsoleJsObject::Setup(
     AdblockPlus::JsEngine& jsEngine, AdblockPlus::JsValuePtr obj)
 {
   obj->SetProperty("error", jsEngine.NewCallback(::ErrorCallback));
   obj->SetProperty("trace", jsEngine.NewCallback(::TraceCallback));
   return obj;
 }