Fixed error saving APNG with duplicate frames and different duration times

[thak1411]

Resolves #5608

This issue is caused by the 'duration' variable being overwritten.

Pillow/src/PIL/PngImagePlugin.py

Line 1120 in 83c05aa

duration = encoderinfo.get("duration", 0)

After being overwritten, the duration variable is not updated.

Pillow/src/PIL/PngImagePlugin.py

Lines 1083 to 1084 in 83c05aa

	if isinstance(duration, (list, tuple)):
	encoderinfo["duration"] = duration[frame_count]

[dogemad]

Yes. There is a problem in that 'duration', which should be passed as an integer to the following context, is passed as a list by redefining the same variable names in lines 1062 and 1120 (if the condition: 1115 ~ 1119 is satisfied, This condition is satisfied when the same frame as the previous frame in the animated image is detected in succession.). So in this case using the round method on the list will throw an error.

[radarhere]

I've created thak1411#1 with some suggestions.

[thak1411]

Thank you for your suggestion. The merge is complete.

[thak1411]

thanks @dogemad @radarhere !