[ROCm][Bugfix] Return empty UUID string when amdsmi uuid query fails

RocmPlatform.get_device_uuid caught AmdSmiException from
amdsmi_get_gpu_device_uuid but did not return, leaving device_uuid
unbound. The trailing `return device_uuid` then raised
UnboundLocalError, masking the original amdsmi error. Return "" on
failure, matching the handling of the preceding handle-query block.

Signed-off-by: Chuan Li <chuali@amd.com>
Co-authored-by: Cursor
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: ChuanLi1101

vllm/platforms/rocm.py

@@ -753,6 +753,7 @@ def get_device_uuid(cls, device_id: int = 0) -> str:
             device_uuid = amdsmi_get_gpu_device_uuid(device)
         except AmdSmiException as error:
             logger.error("amdsmi device uuid query failed ", exc_info=error)
+            return ""
         return device_uuid
 
     @classmethod