Add try catch

With:
```
01:07:54.343 - [failed] [desktop.bundles/index/_index.css] file-copy
01:07:54.343 - [rebuild] [desktop.bundles/index/index.priv.ru.js] priv-js-i18n
01:07:54.344 - build failed
Error: <css input>:451:5: Missing property value
        op1
    }
    ^

    at null.<anonymous> (/home/escaton/www/ny2015/static/node_modules/enb-autoprefixer/techs/css-autoprefixer.js:16:19)
    at resultTechMethods._getBuildResult (/home/escaton/www/ny2015/static/node_modules/enb-autoprefixer/node_modules/enb/lib/build-flow.js:549:34)
    at /home/escaton/www/ny2015/static/node_modules/enb-autoprefixer/node_modules/enb/lib/build-flow.js:596:67
    at Array.0 (/home/escaton/www/ny2015/static/node_modules/enb-autoprefixer/node_modules/enb/node_modules/vow/lib/vow.js:202:56)
    at Object.callFns [as _onImmediate] (/home/escaton/www/ny2015/static/node_modules/enb-autoprefixer/node_modules/enb/node_modules/vow/lib/vow.js:462:35)
    at processImmediate [as _immediateCallback] (timers.js:336:15)
```
without:
```
01:08:13.515 - [failed] [desktop.bundles/index/index.css] css-autoprefixer
01:08:13.516 - [failed] [desktop.bundles/index/_index.css] file-copy
01:08:13.516 - [rebuild] [desktop.bundles/index/index.priv.ru.js] priv-js-i18n
01:08:13.516 - build failed
undefined
```