New VideoCapture is broken (Bug #3880)

Hi, I believe that during the creation of the new videoio module, VideoCapture was broken by using cv::Ptr : When using Direct Show (and most probably any other camera module), isOpened() always reports "true" even if no camera has been opened. This is because in cap.cpp, line 516:

bool VideoCapture::isOpened() const
{
    return (!cap.empty() || !icap.empty());
}

The problem lies in cap.cpp, line 624:

case CV_CAP_DSHOW:
            capture = Ptr<IVideoCapture>(new cv::VideoCapture_DShow(index));
if (capture)
 return capture

Reproducing and explaining the error

1. Write a program containing the lines cv::VideoCapture cap(0) and assert(!cap.isOpened()) and run it with no camera attached
2. In cap.cpp, line 624, cv::VideoCapture_DShow will be instanciated and in its constructor the helping method open() will notice that the number of available devices is 0 and thus leave all member variables to the default (i.e. all to -1)
3. Although the created VideoCapture_DShow is just a dummy, the smart pointer contains a value and thus if(capture) holds and the method returns a capture object
4. One layer higher, back in the VideoCapture::open(int device), this object is assigned to the member variable icap which is then assumed to be a valid, open camera. But it is not!
5. P.S.: The runtime error happens when you try to retrieve an image and in cap_dshow.cpp, line 1591:
   

   bool videoInput::isDeviceSetup(int id){
   
       if(id<devicesFound && VDList[id]->readyToCapture)return true;
       else return false;
   
   }
   

   
   this method is called with the icaps device id - which has the default value -1. thus, VDList[-1] crashes.

Pew, this was a long post containing many problems. I hope I could make my point clear enough :-) . Plus, I fear that the same error might occur in other parts of the new camera module.