Parsing Decimal With Negative Exponent And Zero Scale Can Overflow

**Describe the bug**

This passes as expected
```
let v = parse_decimal::("99999999999999999999999999999999999999", 38, 0).unwrap();
assert_eq!(v, 99999999999999999999999999999999999999);
```

But if we add an additional `9` followed by `e-1` we get overflow

```
let v = parse_decimal::("999999999999999999999999999999999999999e-1", 38, 0).unwrap();
assert_eq!(v, 99999999999999999999999999999999999999);
```

**To Reproduce**

**Expected behavior**

**Additional context**