Trouble with setting up Sponge Forge on Eclipse

Hi, I followed this tutorial to setup sponge forge on eclipse, but I’m getting errors once I run at 5:05 in the video.

  • What went wrong:
    Execution failed for task ‘:recompileMc’.
    /> Cannot invoke “String.split(String)” because “currentExtDirs” is null

How do I fix this? I updated Gradle and tried following along with this article but can’t get past the “Editing the build script” section because I don’t really understand what I’m supposed to do on the article that they send you to.