Unexpected runtime error

The runtime has encountered an unexpected error.

Error source

Page Name:/entry.xsp
Control Id: _id51

Exception

Error while executing JavaScript computed expression
Script interpreter error, line=1, col=39: 'category.getDocument()' is null

JavaScript code

   1: var className=(category.getDocument().getUniversalID()==requestScope.currentPage ||category.getDocument().getUniversalID()==requestScope.activePressBlog || sessionScope.activeCategory==compositeData.categoryUnid)? 'menu-category-sel':'menu-category';
   2: if(className=='menu-category-sel'){
   3: 	if(Content.getAllEntriesByKey(compositeData.categoryUnid,true).getCount()==1){
   4: 		className='menu-category-empty-sel'
   5: 	}
   6: }
   7: return className;

► Stack Trace