Merging layer with opacity < 100% causes crash

[mrtripie]

Pixelorama version:

0.9

OS/device including version:

Widows 10
Gtx 1060 6GB

Issue description:

If you merge a layer that has a cel with < 100% opacity with the layer below, Pixelorama will crash.

Steps to reproduce:
1: make a file
2: add a layer
3: adjust opacity to less than 100%
4: merge with layer below.

[Variable-ind]

I quick tested the web version, i can't seem to reproduce the bug (does it happen on web as well?)

[mrtripie]

Doesn't crash in web editor, however, if I draw in the semi transparent layer there, and merge it, it won't take the opacity into account when merging.

[Variable-ind]

Nevermind i found the bug..., There needs to be selected_layer.lock() added at line 529 of AnimationTimeline.gd

[mrtripie]

That sounds likely to be what would fix the crash, will it also merge with the correct level of opacity?

Here's what I mean in the web editor, the blue square is merged in with 100% opacity when I wanted it to be merged in semi transparently:

2021-09-22.14-47-30.mp4

[Variable-ind]

yeah, selected_layer.lock() fixes the crash along with transparency