[bug?] Doesn't work when chained in a single module.loaders config, but works with multiple.

If I have this webpack config:

``` js
module.exports = {
resolve: {
extensions: [ "", ".js", ".jsx", ".glsl" ]
},
module: {
loaders: [
{ test: /\.jsx?$/, loader: 'babel', exclude: /node_modules/ },
{ test: /\.glsl$/, loader: 'glslify!raw' },
],
},
}
```

compiling a project with .glsl files has error like this:

```
> webpack --progress --colors src/index.js react-famous.js

Hash: a7cef25085d319d4b4ad
Version: webpack 1.12.1
Time: 2166ms
Asset Size Chunks Chunk Names
react-famous.js 1.42 MB 0 [emitted] main
+ 319 hidden modules

ERROR in ./~/famous/webgl-shaders/FragmentShader.glsl
Module build failed: Error: Final loader didn't return a Buffer or String
at DependenciesBlock.onModuleBuild (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:299:42)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:275:25)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:292:15
at runSyncOrAsync (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:160:12)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:290:3)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:292:15
at runSyncOrAsync (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:160:12)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:290:3)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:259:5
at Storage.finished (/home/trusktr/src/pilwon+react-famous/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:38:16)
at evalmachine.:334:14
at /home/trusktr/src/pilwon+react-famous/node_modules/graceful-fs/graceful-fs.js:102:5
at FSReqWrap.oncomplete (evalmachine.:95:15)
@ ./~/famous/webgl-shaders/index.js 28:21-53

ERROR in ./~/famous/webgl-shaders/VertexShader.glsl
Module build failed: Error: Final loader didn't return a Buffer or String
at DependenciesBlock.onModuleBuild (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:299:42)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:275:25)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:292:15
at runSyncOrAsync (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:160:12)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:290:3)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:292:15
at runSyncOrAsync (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:160:12)
at nextLoader (/home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:290:3)
at /home/trusktr/src/pilwon+react-famous/node_modules/webpack-core/lib/NormalModuleMixin.js:259:5
at Storage.finished (/home/trusktr/src/pilwon+react-famous/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:38:16)
at evalmachine.:334:14
at /home/trusktr/src/pilwon+react-famous/node_modules/graceful-fs/graceful-fs.js:102:5
at FSReqWrap.oncomplete (evalmachine.:95:15)
@ ./~/famous/webgl-shaders/index.js 27:19-49
```

but if I instead have this config:

``` js
module.exports = {
resolve: {
extensions: [ "", ".js", ".jsx", ".glsl" ]
},
module: {
loaders: [
{ test: /\.jsx?$/, loader: 'babel', exclude: /node_modules/ },
{ test: /\.(glsl|frag|vert)$/, loader: 'raw' },
{ test: /\.(glsl|frag|vert)$/, loader: 'glslify' },
],
},
}
```

then it works as expected. Any idea why that might be?