LPS-44689  AssetCategoryException is thrown when required category not checked 

Hi Hugo,

As for the AssetCategoryException and AssetTagException, knowledgebase portlet will thrown the info directly"javax.portlet.PortletException: com.liferay.portlet.asset.AssetCategoryException
javax.portlet.PortletException: com.liferay.portlet.asset.AssetCategoryException" in log instead of using asset_categories_error/page.jsp.

I check the code and find AssetCategoryException and AssetTagException didn't be judged(catch or handle with them) in isSessionErrorException method (for example, DisplayPortlet.isSessionErrorException). 

By adding the fix code, knowledge portlet will use the same method with portal to handle with the two exception(/html/taglib/ui/asset_categories_error/page.jsp)

Thanks,
Hai