Handle when no batch sampler (coqui-ai#1882)

TTS/tts/models/vits.py

@@ -1613,14 +1613,24 @@ def get_data_loader(
 
             # get samplers
             sampler = self.get_sampler(config, dataset, num_gpus)
-
-            loader = DataLoader(
-                dataset,
-                batch_sampler=sampler,
-                collate_fn=dataset.collate_fn,
-                num_workers=config.num_eval_loader_workers if is_eval else config.num_loader_workers,
-                pin_memory=False,
-            )
+            if sampler is None:
+                loader = DataLoader(
+                    dataset,
+                    batch_size=config.eval_batch_size if is_eval else config.batch_size,
+                    shuffle=False,  # shuffle is done in the dataset.
+                    collate_fn=dataset.collate_fn,
+                    drop_last=False,  # setting this False might cause issues in AMP training.
+                    num_workers=config.num_eval_loader_workers if is_eval else config.num_loader_workers,
+                    pin_memory=False,
+                )
+            else:
+                loader = DataLoader(
+                    dataset,
+                    batch_sampler=sampler,
+                    collate_fn=dataset.collate_fn,
+                    num_workers=config.num_eval_loader_workers if is_eval else config.num_loader_workers,
+                    pin_memory=False,
+                )
         return loader
 
     def get_optimizer(self) -> List: