update m2pool 修复opai 接口文档中获取挖矿账户和矿工对应算力为空，设置单位的空指针问题

m2pool-modules/m2pool-oapi/src/main/java/com/m2pool/oapi/service/impl/MinerServiceImpl.java

@@ -42,8 +42,10 @@ public class MinerServiceImpl implements MinerService {
         }
 
         HashRateRealDto dto = minerMapper.getMinerRealHashRateByCoinAndAccountMiner(vo);
+        if (dto != null){
+            dto.setUnit(unit.getUnit());
+        }
 
-        dto.setUnit(unit.getUnit());
         return AjaxResult.success(dto);
     }