Update createTree to use correct parameters

[benbean303]

Fixes #6196

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[mvaligursky]

Looks good to me, thanks!
Has it completely solved you issue @benbean303 ?

[benbean303]

There's still a couple of issues when running a nested blend tree that I haven't been able to crack:

• An error related to syncAnimations when enabled, since it's trying to blend each child's anim track but blendshapes themselves shouldn't have an assigned animation. Can be avoided by setting syncAnimations to false.
• Similarly in the calculateWeights function, it's attempting to set the weight of each child, however blend trees do not have a setter for weight. (reference photo below)

Adding a setter in resolves the error, but skeleton positions seem to collapse into their origin:

I'm not sure if I'm going about this wrong or not. I've been doing most of my tests in this project: https://playcanvas.com/project/1202797/overview/blend-tree-testing