SAK-18919 return a 404 rather than throwing an error

git-svn-id: https://source.sakaiproject.org/svn/portal/trunk@80984 66ffb92e-73f9-0310-93c1-f5514f145a0a

portal/portal-tool/tool/src/java/org/sakaiproject/portal/tool/ToolPortal.java

@@ -139,7 +139,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse res)
 					+ req.getServletPath() + "/" + placementId, toolPath);
 
 		}
-		catch (Throwable t)
+		catch (Exception t)
 		{
 			doError(req, res, t);
 		}