When window is open, ts=0, calculation error

**Bug Description**

When window is open, ts=0, calculation error
+ case
```yaml
- id: 1
desc: ts列的值为0
inputs:
- columns: [ "c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date" ]
indexs: [ "index1:c1:c7" ]
rows:
- [ "aa",20,30,1.1,2.1,0,"2020-05-01" ]
- [ "aa",21,31,1.2,2.2,0,"2020-05-02" ]
- [ "aa",22,32,1.3,2.3,1590738992000,"2020-05-03" ]
- [ "aa",23,33,1.4,2.4,1590738993000,"2020-05-04" ]
- [ "bb",24,34,1.5,2.5,1590738994000,"2020-05-05" ]
sql: |
SELECT c1, c3, sum(c4) OVER w1 as w1_c4_sum FROM {0} WINDOW w1 AS (PARTITION BY {0}.c1 ORDER BY {0}.c7 ROWS_RANGE BETWEEN 2s PRECEDING AND 0s OPEN PRECEDING EXCLUDE CURRENT_TIME);
expect:
order: c3
columns: [ "c1 string","c3 int","w1_c4_sum bigint" ]
rows:
- [ "aa",20,null ]
- [ "aa",21,null ]
- [ "aa",22,null ]
- [ "aa",23,32 ]
- [ "bb",24,null ]
```

**Expected Behavior**

**Relation Case**
test_current_row.yaml id:13