Indexed Transparent Images not WYSIWYG

[RyanBram]

Hi Developer, I found an issue for producing indexed images with transparent background using mtPaint 3.4.0. I used option Image -> Convert To Indexed ... -> OK, with palette selected to "PNN Quantize (slow, better quality)" and Dither to "None". mtPaint 3.4.0 is capable to do that without losing transparencies in my image. But when I want to save the image as PNG or GIF, the result will has random background, even though in the mtPaint canvas it doesnt' has. I also attach the image that I mentioned.