Grunt Less task breaks on compiling sprites.less generated from grunt-spritesmith

[vehdad]

Sorry for opening issue but I am stuck with old app running number of grunt tasks, among others grunt-contrib-less for less files and grunt-spritesmith for building sprites.

After updating to the less 3.0.0 I updated to the grunt-contrib-less: 2.0.0 and spritesmith accordingly to the 6+ version.

When I run less task it breaks on sprites.less on line:
@spritesheet: 576px 576px '../../img/icons.png' @spritesheet-sprites;
with an error
[L472:C0] Cannot read property 'eval' of null

Running "less:dev" (less) task

src\assets\style\cando-ui\sprites.less: [L472:C0] Cannot read property 'eval' of null
Warning: Error compiling src/assets/style/style.less Use --force to continue.

All dependencies are met..

-- grunt@1.0.4
-- grunt-contrib-less@2.0.0
-- grunt-spritesmith@6.6.3
-- grunt-cli@1.3.2

[vehdad]

After some investigation, I think problem is in part where sprites.less is generated and not in this module. I apologize for opening issue here.

[vehdad]

Sorry, It actually seems to be on this part at the end.

Task keeps breaking after all changes and even after grunt-spritesmith has been fixed and updated by owner.

Running "less:dist-app" (less) task

undefined: [Lundefined:Cundefined] Cannot read property 'eval' of null
Warning: Error compiling build/css/style/style.less Use --force to continue.

File style.less has only two lines - imports.

@import "my-ui/custom";
@import (inline) "css/bootstrap.css";