Bug 281126 [CSS] Illegal state exc from tab-height
If you just type a space in the CSS Editors SWT example you will get traces in the console failing on CSSValue.getFloatValue() for tab-height.
bundles/org.eclipse.e4.ui.css.swt/src/org/eclipse/e4/ui/css/swt/properties/custom/CSSPropertyCTabFolderTabHeightHandler.java
AbstractCSSPropertySWTHandler {
	public static final ICSSPropertyHandler INSTANCE = new CSSPropertyCTabFolderTabHeightHandler();
	
	@Override
	protected void applyCSSProperty(Control control, String property,
			CSSValue value, String pseudo, CSSEngine engine) throws Exception {
		if ((value.getCssValueType() == CSSValue.CSS_PRIMITIVE_VALUE)) {
			int height = (int) ((CSSPrimitiveValue) value).getFloatValue(CSSPrimitiveValue.CSS_PX);
			if (control instanceof CTabFolder) {
				CTabFolder folder = (CTabFolder) control;
				folder.setTabHeight(height);
			}
		}
		
	}
	@Override
	protected String retrieveCSSProperty(Control control, String property,
			String pseudo, CSSEngine engine) throws Exception {
		if (control instanceof CTabFolder) {
			CTabFolder folder = (CTabFolder)control;
			return Integer.toString( folder.getTabHeight());
		}
		return null;
	}
}