AnimationTree throwing get and set errors for Parameter "process_state" is null

[MarkoZlender]

Tested versions

• Reproducible in: v4.4.rc1.official [8ed125b]
• Not reproducible in: v4.3.stable.mono.official [77dcf97]

System information

Windows 11 Pro Version 24H2 26.‎1.‎2025. OS build 26100.2894 Experience Windows Feature Experience Pack 1000.26100.36.0
CPU: AMD R7 7800X3D
GPU: Radeon RX 7900 XTX, Driver version: 24.12.1

Issue description

Whenever I start moving the character in a different direction I get the following errors over and over again:

E 0:00:02:774 set_parameter: Parameter "process_state" is null. <C++ Source> scene/animation/animation_tree.cpp:73 @ set_parameter()
E 0:00:02:774 get_parameter: Parameter "process_state" is null. <C++ Source> scene/animation/animation_tree.cpp:93 @ get_parameter()

This doesn't seem to break anything and everything works as intended but I don't know why are the errors happening.

Steps to reproduce

AnimationTree with CharacterBody3D node as Advance Expression Base Node which defines the velocity parameter for advance_expression as shown in MRP.

Minimal reproduction project (MRP)

topdown.zip

[matheusmdx]

Reverting pr #100039 fixes the issue, CC @TokageItLab

[EdMalovnek]

Im experiencing this issue in stable 4.4 now.

Errors dont seem to break anything, but logs are flooded with

E 0:00:02:482   get_parameter: Parameter "process_state" is null.
  <C++ Source>  scene/animation/animation_tree.cpp:93 @ get_parameter()

E 0:00:02:482   set_parameter: Parameter "process_state" is null.
  <C++ Source>  scene/animation/animation_tree.cpp:73 @ set_parameter()