Illegal UTF8 String? - Solved by me(thanks for trying to help anyway)

So I was making a mod using MCreator 1.7.9 and opened up MCreator today. I don't know what it means, but I am out of no where getting this error:

:sourceMainJava
:compileJava FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':compileJava'.
> Illegal UTF8 string in constant pool in class file com/sun/tools/javac/util/BasicDiagnosticFormatter
 

Any idea on how to fix this?

Edit:

Okay, I fixed it. All I did was download a clean version of mcreator, and copied all of the files from the other one that I had into the clean version. I do not know how it fixed it, but it did.