texture.getSource Failed to load resource - the server responded with a status of 400

Hi, please whenever i try to use the texture.getSource() function, i always get this error:
“Failed to load resource: the server responded with a status of 400 ()”
here is the link of the project you can find the script in the js file called “JS_MDL_scatterMapMask.js”
https://playcanvas.com/project/1306915/overview/public-test
thanks in advance!