Image _handleImageFrame execute twice when has cache

[weiminghuaa]

🐛 Bug Report

Image _handleImageFrame execute twice when has cache, it's not happend on Image.network, because MultiImageStreamCompleter addListener not check currentImage.

// MultiFrameImageStreamCompleter
@override   
void addListener(ImageStreamListener listener) {     
    if (!hasListeners && _codec != null && (_currentImage == null || _codec!.frameCount > 1))       
        _decodeNextFrameAndSchedule();     
    super.addListener(listener);   
}  

// MultiImageStreamCompleter 
@override   
void addListener(ImageStreamListener listener) {   
    if (!hasListeners && _codec != null) _decodeNextFrameAndSchedule();    
    super.addListener(listener);  
}

Expected behavior

Reproduction steps

Configuration

Version: 3.1.0

Platform:

• [ ] :iphone: iOS
• [ ] :robot: Android