Merge branch 'blender-v2.90-release'

Fix T79453: Motion Tracking: marker does not remember 'enabled' state

Caused by rB63ee3db96107.

While above commit corrected the clip offset, it also removed logic to
ensure a marker on a particular frame. This is needed though, otherwise
changes on a particular frame are applied to the marker being returned
by 'BKE_tracking_marker_get' which can be a completely different marker
if none exist for that frame yet.

This patch partly reverts rB63ee3db96107 and reintroduces the framenr
for the MarkerUpdateCb and uses that to ensure a marker on that frame.

Candidate for backporting to 2.83 LTS?

Reviewers: sergey, jacqueslucke

Subscribers:

Merge branch 'blender-v2.90-release'

Fix T78536: Crash calling object.modifier_apply on an empty

Caused by rB6add0cc88a0d.

Maniphest Tasks: T78536

Differential Revision: https://developer.blender.org/D8440

Merge branch 'blender-v2.90-release'

Fix T79111: Cycles: Image Sequence not rendering

Caused by c7aa0f9d743ee9cafe91b4a51d9f1ecc5e437d71.

Since above commit, BKE_image_user_frame_calc requires an image (not
just the iuser) to get the framenumber.

Cycles used to call this with NULL image (in `image_user_file_path` and
`image_user_frame_number`), now pass the image as well.

Maniphest Tasks: T79111

Differential Revision: https://developer.blender.org/D8439

Merge branch 'blender-v2.90-release'

UI: fix buttons ranges not properly updated when tabbing to next/previous
button

This was reported for the FCurve modifier restrict ranges, but might fail
elsewhere, too. Reason is that the post_but has its range (hardmin/
hardmax etc) set before the updates to the active button take place, so
changes here dont end up on the post_but (even though the RNA range
function is properly called for a new defined button - new one is not the
same as the post_but though).

Now update the ranges on the post_but when that gets active.

Fixes T78763

Maniphest Tasks: T78763

Differential Revision: https://developer.blender.org/D8265

Merge branch 'blender-v2.90-release'

Fix T79357: VSE crash on prefetching when performing cuts

Caused by {rBa1a333a1e92e}

`BKE_sequencer_prefetch_get_original_sequence` cant get a sequence in
`BKE_sequencer_cache_put`.

rBa1a333a1e92e moved multiple NULL checks (including the one checking
seq) above BKE_sequencer_prefetch_get_original_sequence (this should
never return NULL really, but this is for another fix).

So solution suggested by @ISS is to just stop prefetching all together
before changing content of seqbase.

Maniphest Tasks: T79357

Differential Revision: https://developer.blender.org/D8421