ZK7 - Unexpected token in DSP/CSS

problem:
i have reported a problem in ticket IDEMPIERE-2496. This issue happening well, maybe found root cause, hope by analysing generated css code.

tested:
i have tested idempiere version: 3.0.0.v20150326-0015

1. open google chrome
2. login to gardenworld
3. open developer tools>>source >> navigate to theme css (copy > save > attached here)
4. paste to http://csslint.net/ - see result 5 errors - > 3x TOKEN ISSUE

EXAMPLE PROBLEM - no font family generated
.z-treecell-content {
font-family: ;
font-size: 11px;
}

causeed by
~/css/fragment/tree.css.dsp

<%@ taglib uri="http://www.zkoss.org/dsp/web/core" prefix="c" %>
.z-treecell-content {
font-family: ${croperty('org.zkoss.zul.theme.fontFamilyC')};
font-size: ${croperty('org.zkoss.zul.theme.fontSizeM')};
}