fix CollectionNotExist on describe rg (#26541)

Signed-off-by: Wei Liu <wei.liu@zilliz.com>

internal/proxy/task.go

@@ -2211,11 +2211,16 @@ func (t *DescribeResourceGroupTask) Execute(ctx context.Context) error {
 	getCollectionName := func(collections map[int64]int32) (map[string]int32, error) {
 		ret := make(map[string]int32)
 		for key, value := range collections {
-			name, err := globalMetaCache.GetCollectionName(ctx, GetCurDBNameFromContextOrDefault(ctx), key)
+			name, err := globalMetaCache.GetCollectionName(ctx, "", key)
 			if err != nil {
 				log.Warn("failed to get collection name",
 					zap.Int64("collectionID", key),
 					zap.Error(err))
+
+				// if collection has been dropped, skip it
+				if common.IsCollectionNotExistError(err) {
+					continue
+				}
 				return nil, err
 			}
 			ret[name] = value

internal/proxy/task_test.go

@@ -3115,7 +3115,9 @@ func TestDescribeResourceGroupTaskFailed(t *testing.T) {
 		},
 	}, nil)
 	err = task.Execute(ctx)
-	assert.Error(t, err)
+	assert.NoError(t, err)
+	assert.Len(t, task.result.ResourceGroup.NumOutgoingNode, 0)
+	assert.Len(t, task.result.ResourceGroup.NumIncomingNode, 0)
 }
 
 func TestCreateCollectionTaskWithPartitionKey(t *testing.T) {