It looks like between iOS 12.01 and 12.1 the PHImageFileURLKey went missing from the info dictionary passed in to the result handler block of [PHImageManager requestImageForAsset: targetSize: contentMode: options: resultHandler:]. It only seems to happen when loading PNG images from thge photo library. The request call spits out the following to the console:
JPEGDecompressSurface : Picture decode failed: e00002c7
[ImageManager] FigPhotoDecompressionContainerDecodeImageForIndexAsync -[PLFigPreheatItem startPreheatRequestWithCompletionHandler:]_block_invoke_2 returned -536870201 from /var/mobile/Media/PhotoData/Thumbnails/V2/DCIM/100APPLE/IMG_0715.PNG/5005.JPG
It may not mean anything, because it is presumably looking for the jpeg thumbnail, but this error did not occur on iOS12.01