BUG: Fixed length check, after slpice(), `l` was wrong

[AlexisWilke]

Q	A
Bug fix?	yes
New feature?	no
Breaking change?	no
Deprecations?	no
Tests added?	no
Fixed issues	n.a.
License	Apache-2.0

The for() loop was setting l as the length of the array. Then within the array you splice() it whenever a filename gets removed. l is now the wrong length. I suggest we simply use the sourceFiles.length so that way it works as expected. We could also reduce l each time a splice() happens.

To test, I used a console.log(sourceFile) inside the loop and I have a README.md file in my package directory. That means a splice() occurs and you see an undefined in your console for the last i which is larger than sourceFiles.length.