[BugFix] Fix ascend scheduler assert error (#3191)

### What this PR does / why we need it?
Running multimodal model with ascend scheduler may cause assert error
【assert (request.num_tokens - request.num_computed_tokens) == 1】

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?


- vLLM version: v0.10.2
- vLLM main:
17b4c6685c

---------

Signed-off-by: fan2956 <zhoufan53@huawei.com>

vllm_ascend/core/scheduler.py

@@ -214,7 +214,8 @@ class AscendScheduler(Scheduler):
                      new_encoder_budget) = self._try_schedule_encoder_inputs(
                          request, num_computed_tokens, num_new_tokens,
                          encoder_budget)
-                if num_new_tokens == 0:
+                    if num_new_tokens == 0 or len(
+                            encoder_inputs_to_schedule) == 0:
                         # The request cannot be scheduled.
                         break