Fixed using info dictionary when writing multiple APNG frames

[radarhere]

Two changes here.

1. Fixed using info dictionary when writing multiple APNG frames.

duration can come from encoderinfo or info when saving multiple frames.

Pillow/src/PIL/PngImagePlugin.py

Line 1062 in 696b82e

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

The duration variable is only part of the individual frame's encoderinfo when it is a list or tuple though, or if it was part of the actual image's encoderinfo.

Pillow/src/PIL/PngImagePlugin.py

Lines 1082 to 1084 in 696b82e

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

So when it comes to fetch it for writing, it is ignored.

Pillow/src/PIL/PngImagePlugin.py

Line 1153 in 696b82e

disposal = frame_data["encoderinfo"].get("disposal", APNG_DISPOSE_OP_NONE)

The same applies to disposal and blend.

2. Pillow/src/PIL/PngImagePlugin.py

   Lines 1122 to 1125 in 696b82e

   	if "duration" in previous["encoderinfo"]:
   	previous["encoderinfo"]["duration"] += frame_duration
   	else:
   	previous["encoderinfo"]["duration"] = frame_duration

Duration is either specified for every frame (in which case the condition is true), or a single value is used (in which case previous["encoderinfo"]["duration"] = frame_duration is unnecessary). So the else code can be removed.