Drag and dropping bitmap images (as in drag and dropping directly from
another software such as a web browser, not from an image file in
Finder) inside the Blender window on macOS would segfault due to the
dropped image being [autorelease]d even though its data was meant to
outlive the function scope.
Fixed by removing the superflous autorelease and adding a comment note.
The only caller of this function (GHOST_SystemCocoa::handleDraggingEvent)
already properly [release]s the image in question.
Note that currently, non-file/bitmap image drag and drop is not
implemented on the WM side, and as such this feature/GHOST event does
not do anything practical.
Pull Request: https://projects.blender.org/blender/blender/pulls/135076
8f1d03cd75