BUG: Error in integration with Seurat v5 after subsetting specific cluster

[K-S-J-P]

Issue Description

Hi, I'm working on the analysis with Seurat v5 and have an issue on integrative analysis in Seurat v5.
I have a large Seurat object consisting multiple cell types and want to try to subset a specific cluster (CD4T) and do subclustering.
When I try to do IntegrateLayers on this subset after doing NormalizeData/FindVariableFeatures/ScaleData/RunPCA on this subcluster, I get an error message like
"The 'features' argument is ignored by 'HarmonyIntegration'.
This message is displayed once per session.
Error in names (groups) <- "group" : attempt to set an attribute on NULL."

When I used the same code 2 weeks ago, it worked but now it does not. The only change is that I used different seurat cluster number information from meta.data for this subcluster. I used cluster number in "seurat_cluster" within metadata 2 weeks ago, but now I want to use the cluster number from another cluster information (this case is "RNA_snn_res0.3"). So before I extract the subcluster, I changed active.ident from "seurat_cluster" to "RNA_snn_res0.3". Could this be the reason for this error? I've attached the error message and sessionInfo.

If someone has an idea on that, I would greatly appreciate it in advance. Thank you for your help.

Reproducing Code Example

Idents(merged_seurat) <- "RNA_snn_res.0.3"
CD4T <- subset(x = merged_seurat, idents = c('3'))

#Normalizing the data
CD4T <- NormalizeData(CD4T, normalization.method = "LogNormalize", scale.factor = 10000)

#Identification of highly variable features (feature selection)
CD4T <- FindVariableFeatures(CD4T)
CD4T <- ScaleData(CD4T, verbose = FALSE)
CD4T <- RunPCA(CD4T)

#Integration
CD4T <- IntegrateLayers(CD4T, method = HarmonyIntegration, orig.reduction = "pca", new.reduction = "harmony", verbose = FALSE)

Error Message

"The 'features' argument is ignored by 'HarmonyIntegration'. 
This message is displayed once per session. 

Error in names (groups) <- "group" : attempt to set an attribute on NULL."

Additional Comments

No response

Session Info

please see attached file