Exported images from the preview of a grayscale/float outputting node only have a red channel set

[mieldepoche]

Material Maker version:
1.4a2 from itch

OS/device including version:
windows 11

Issue description:

in the preview	exported file

When trying to export an image that results from a grayscale (float) output, the rendered image only has a red channel.

Steps to reproduce:

{"connections":[{"from":"uniform_greyscale","from_node":"node_uniform_greyscale","from_port":0,"keep_alive":false,"to":"combine","to_node":"node_combine","to_port":0},{"from":"uniform_greyscale","from_node":"node_uniform_greyscale","from_port":0,"keep_alive":false,"to":"combine","to_node":"node_combine","to_port":1},{"from":"uniform_greyscale","from_node":"node_uniform_greyscale","from_port":0,"keep_alive":false,"to":"combine","to_node":"node_combine","to_port":2}],"nodes":[{"color":{"a":1.0,"b":0.0,"g":0.0,"r":0.0,"type":"Color"},"name":"comment","node_position":{"x":-287.0,"y":-114.75},"parameters":{},"seed_int":0,"size":{"x":249.0,"y":164.0},"text":"float -> only red channel","title":"Comment","type":"comment"},{"color":{"a":1.0,"b":0.0,"g":0.0,"r":0.0,"type":"Color"},"name":"comment_2","node_position":{"x":73.0,"y":-114.75},"parameters":{},"seed_int":0,"size":{"x":179.0,"y":245.0},"text":"color -> works fine","title":"Comment","type":"comment"},{"name":"uniform_greyscale","node_position":{"x":-265.0,"y":-42.75},"parameters":{"color":0.5},"seed_int":0,"type":"uniform_greyscale"},{"name":"combine","node_position":{"x":95.0,"y":-42.75},"parameters":{},"seed_int":0,"type":"combine"}]}