ERROR in Path must be a string. Received undefined

Im trying to use Splunk parallel-piper, and followed all the docuemntation, however when I build my Node.Js, I receive an error message that Im not able to solve it.

Any guidance is appreciated:

    sh build.sh

43% 23/41 build modulesThe unused option is deprecated. Please use options.discardUnused instead.
The urls option is deprecated. Please use options.normalizeUrl instead.
The idents option is deprecated. Please use options.mergeIdents instead.
The idents option is deprecated. Please use options.reduceIdents instead.
Hash: c39b586fc444f14cb888
Version: webpack 1.13.1
Time: 3855ms
Asset Size Chunks Chunk Names
9cbe61a2b483128aadcd2d38d9a51fa6.svg 36.7 kB [emitted]
d39c7c45536d58b6d370d09b74b37bfa.eot 11.7 kB [emitted]
3b777c30a2fc8ad75220c4b86556c5eb.ttf 21.9 kB [emitted]
23ed833c737fb20e3138ec99fd1db0df.woff 13.5 kB [emitted]
piper.js 131 kB 0 [emitted] main
piper.css 7.41 kB 0 [emitted] main
index.html 52 bytes [emitted]
+ 154 hidden modules

WARNING in piper.js from UglifyJs
Condition always true [.//jquery/dist/jquery.js:9778,0]
Dropping side-effect-free statement [.//virtual-dom/virtual-hyperscript/index.js:123,0]

ERROR in Path must be a string. Received undefined`

[YannickNoPanic]

If anyone finds this and is still dealing with this:
webpack/css-loader#126 this is basically the same
webpack/css-loader@3d2435c this is the solution

[ohmyguigs]

I made a workaround like this:
SplunkGlobalDevs/SplunkMeetup-BiscoitoVsBolacha@e0ec911

tldr;
Adding publicPath: '' in output of webpack.config