Only handle scroll events when PDFView.pdfDocument is defined (issue 4642)
Version 1.0.68
PDFImage_resize: copy in place with alpha and ~5x speed up
Merge pull request #4663 from yurydelendik/v1.0.68

Version 1.0.68
Merge pull request #4645 from Snuffleupagus/issue-4642

Only handle scroll events when PDFView.pdfDocument is defined (issue 4642)
Merge pull request #4666 from p01/Faster_image_resize

PDFImage_resize: copy in place with alpha and ~5x speed up