Image not exporting until an extension is added manually to filename

[williamchange]

Material Maker version:

1.4a3 @ 337de18

OS/device including version:

Macbook M1 Sequoia 15.3.1

Issue description:

Image file does not export correctly until an extension (i.e. .png) is added to the file name.

With the ".png" option next to the file name, I expect the extension would be appended to the file name but this doesn't seem to be the case

Steps to reproduce:
Select a folder and attempt to export an image from the 2D Preview panel:

out.mp4