fix data sample is None

Author: xiexinch

mmseg/models/data_preprocessor.py

@@ -137,7 +137,7 @@ def forward(self, data: dict, training: bool = False) -> Dict[str, Any]:
                 'as the image size might be different in a batch')
             # pad images when testing
             if self.test_cfg:
-                inputs, data_samples = stack_batch(
+                inputs, _ = stack_batch(
                     inputs=inputs,
                     size=self.test_cfg.get('size', None),
                     size_divisor=self.test_cfg.get('size_divisor', None),