Compilation fix (removes possible warning)

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@4019 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/datasrc/zonetable.cc

@@ -89,6 +89,8 @@ struct ZoneTable::ZoneTableImpl {
             // Can Not Happen
             default:
                 assert(0);
+                // Because of warning
+                return (FindResult(result::NOTFOUND, ConstZonePtr()));
         }
 
         // Can Not Happen (remember, NOTFOUND is handled)