Fix to work with validation dataset

library/train_util.py

@@ -2403,6 +2403,7 @@ class ControlNetDataset(BaseDataset):
 
         self.dreambooth_dataset_delegate = DreamBoothDataset(
             db_subsets,
+            True,
             batch_size,
             resolution,
             network_multiplier,

sdxl_train_textual_inversion.py

@@ -1,5 +1,6 @@
 import argparse
 import os
+from typing import Optional, Union
 
 import regex
 
@@ -23,7 +24,8 @@ class SdxlTextualInversionTrainer(train_textual_inversion.TextualInversionTraine
         sdxl_train_util.verify_sdxl_training_args(args, supportTextEncoderCaching=False)
 
         train_dataset_group.verify_bucket_reso_steps(32)
-        val_dataset_group.verify_bucket_reso_steps(32)
+        if val_dataset_group is not None:
+            val_dataset_group.verify_bucket_reso_steps(32)
 
     def load_target_model(self, args, weight_dtype, accelerator):
         (