fix bug

mallinkService/src/main/java/com/iformall/service/impl/WxCouponServiceImpl.java

@@ -971,7 +971,7 @@ public class WxCouponServiceImpl implements WxCouponService {
         	}else {
         		merchantIds = wxCouponMerchantMapper.findMerchantByProductIds(tenantEntity.getTenantId(),couponIds);
         	}
-        	if (null == merchantIds) {
+        	if (null == merchantIds || merchantIds.size() <= 0) {
         		return couponMerchantMap;
         	}
             WxMerchant merchantQ = new WxMerchant();