fix: fix one more bug from merging mm_inputs (#5718)

Co-authored-by: Xinyuan Tong <justinning0323@outlook.com>
Co-authored-by: XinyuanTong <115166877+JustinTong0323@users.noreply.github.com>

python/sglang/srt/managers/schedule_batch.py

@@ -351,7 +351,6 @@ class MultimodalInputs:
         optional_args = [
             "mm_items",
             "image_pad_len",
-            "mrope_position_delta",
         ]
         for arg in optional_args:
             self_arg = getattr(self, arg, None)
@@ -367,6 +366,14 @@ class MultimodalInputs:
                     [self.mrope_positions, other.mrope_positions], dim=1
                 )
 
+        mrope_position_delta = self.mrope_position_delta
+        if mrope_position_delta is not None:
+            if other.mrope_position_delta is None:
+                self.mrope_position_delta = mrope_position_delta
+            else:
+                self.mrope_position_delta = torch.cat(
+                    [self.mrope_position_delta, other.mrope_position_delta], dim=0
+                )
         # other args would be kept intact
 
 
@@ -1455,7 +1462,6 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
         if self.model_config.is_encoder_decoder:
             self.encoder_lens = torch.cat([self.encoder_lens, other.encoder_lens])
             self.encoder_lens_cpu.extend(other.encoder_lens_cpu)
-
         self.req_pool_indices = torch.cat(
             [self.req_pool_indices, other.req_pool_indices]
         )