if a css or LESS contains a refernce to an image file with @ in it's name, it does not get resolved to fully qualified path
example:
```
.fp-play{background-image:url(img/black@x2.png}
```
Comments: In BundleTransformer 1.6.18 fixed this error.
example:
```
.fp-play{background-image:url(img/black@x2.png}
```
Comments: In BundleTransformer 1.6.18 fixed this error.