Particles rendered incorrectly with a gradient texture

[Chaosus]

Godot version

9f9210e

System information

Windows 11

Issue description

I found that one of particles shaders in my project begin working incorrectly after the recent fixes. I've bisected it to 9f9210e.

Before:

After:

Steps to reproduce

Download the provided test project and compare changes with different version.

Minimal reproduction project

bug.zip

[YuriSizov]

I've bisected it to 9f9210e

Regression from #81137. cc @KoBeWi @Geometror

[KoBeWi]

When I convert the material to ShaderMaterial it works correctly 🤔

EDIT:
Some more findings. It also works when you copy the texture, clear Color Ramp and paste the texture again. Interestingly, it works until editor restart; reloading the scene does not break it. Modifying the texture to send the changed signal does not work.

EDIT2:
Once you "fix" the texture, the particles will correctly update when you modify the texture.