Fix #37119: MCE: Prefetching doesn't fetch last frame of an image-sequence.

Silly mistake in final condition. Now it works fine.

Would be nice to have this for the final release, simple oneliner.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60814 954f8c5b-7b00-dc11-b283-0030488c597c