Fix plan cache core issue caused by failed add plan

src/sql/plan_cache/ob_i_lib_cache_node.cpp

@@ -128,6 +128,9 @@ int ObILibCacheNode::add_cache_obj(ObILibCacheCtx &ctx,
       LOG_DEBUG("succ to add cache obj", KPC(obj));
     }
   }
+  if (OB_FAIL(ret) && ret != OB_SQL_PC_PLAN_DUPLICATE) {
+    is_invalid_ = true;
+  }
   return ret;
 }